Photoresist composition and process for producing photoresist pattern

ABSTRACT

A photoresist composition comprising
     a resin which comprises a structural unit represented by the formula (I):   

     
       
         
         
             
             
         
       
     
     and
     a salt represented by the formula (B1):

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2017-123230 filed in JAPAN on Jun. 23, 2017,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a photoresist composition and a processfor producing a photoresist pattern.

BACKGROUND OF THE INVENTION

JP2008-076747A1 mentions a composition which comprises a resin havingthe following structural unit and the following acid generator.

SUMMARY OF THE INVENTION

The present invention relates to the followings:

<1> A photoresist composition comprisinga resin which comprises a structural unit represented by the formula(I):

wherein R¹ represents a hydrogen atom or a methyl group,R² represents a C1-C6 hydrocarbon group,Ar represents a C6-C36 divalent aromatic hydrocarbon group in whicha hydrogen atom can be replaced by a substituent,R³ represents a hydrogen atom or an acid-labile group; anda salt represented by the formula (B1):

wherein Q^(b1) and Q^(b2) independently each represent a fluorine atomor a C1-C6 perfluoroalkyl group,L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group has been replaced by —CO—, in which a methylene groupcan be replaced by —O— and in which a hydrogen atom can be replaced by afluorine atom or a hydroxyl group,Y represents a methyl group in which a hydrogen atom can be replaced bya substituent or a C3-C18 alicyclic hydrocarbon group in which ahydrogen atom can be replaced by a substituent and in which a methylenegroup can be replaced by —O—, —S(O)₂— or —CO—, and Z⁺ represents anorganic cation.<2> The photoresist composition according to <1>wherein the acid-labile group is represented by formula (1a) or (2a):

in which R^(aa1), R^(aa2) and R^(aa3) independently each represent aC1-C8 alkyl group in which a hydrogen atom can be replaced by asubstituent, a C3-C20 alicyclic hydrocarbon group in which a hydrogenatom can be replaced by a substituent, “naa” represents an integer of 0or 1, and * represents a binding position;

in which R^(aa1′) and R^(aa2′) independently each represent a hydrogenatom or a C1-C12 hydrocarbon group, and R^(aa3′) represents a C1-C20hydrocarbon group, X^(a) represents an oxygen atom or a sulfur atom,and * represents a binding position.<3> The photoresist composition according to <1> or <2> wherein Arrepresents a phenylene group.<4> The photoresist composition according to any one of <1> to <3>wherein R³ represents a hydrogen atom or a group represented by formula(2a).<5> The photoresist composition according to any one of <1> to <4>wherein the resin further comprises a structural unit having anacid-labile group.<6> The photoresist composition according to <5>wherein the structural unit having an acid-labile group is representedby formula (a1-1) or (a1-2):

wherein L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7 and* represents a binding position to —CO—,R^(a4) and R^(as) each independently represent a hydrogen atom or amethyl group,R^(a6) and R^(a7) each independently represent a C1-C8 alkyl group, aC3-C18 alicyclic hydrocarbon group, or a group formed by combining them,m1 represents an integer of 0 to 14,n1 represents an integer of 0 to 10 andn1′ represents an integer of 0 to 3.<7> The photoresist composition according to <6>wherein the resin further comprises the structural unit represented byformula (a1-1) and the structural unit represented by formula (a1-2).<8> The photoresist composition according to any one of <1> to <7> whichfurther comprises a salt generating an acid weaker in acidity than anacid generated from the acid generator.<9> The photoresist composition according to any one of <1> to <8> whichfurther comprises a resin which comprises a structural unit having afluorine atom.<10> A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

(1) a step of applying the photoresist composition according to any oneof <1> to <9> on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film, thereby forming aphotoresist pattern.

DESCRIPTION OF EMBODIMENTS

The photoresist composition of the disclosure comprises a resin whichcomprises a structural unit represented by the formula (I) and a saltrepresented by the formula (B1). Hereinafter, the resin and the salt arereferred to as “resin (A)” and “salt (B1)”, respectively.

Preferably, the photoresist composition further comprises a quencherand/or a solvent.

<Resin (A)>

Resin (A) comprises a structural unit represented by the formula (I):

wherein R¹ represents a hydrogen atom or a methyl group,

R² represents a C1-C6 hydrocarbon group,

Ar represents a C6-C36 divalent aromatic hydrocarbon group in which ahydrogen atom can be replaced by a substituent,

R³ represents a hydrogen atom or an acid-labile group.

Hereinafter, the structural unit represented by formula (I) is sometimesreferred to as “the structural unit (I)”.

For R², examples of the hydrocarbon group include a C1-C6 alkyl groupsuch as a methyl group, an ethyl group, a propyl group, a butyl group,an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentylgroup and a hexyl group; a C3-C6 cycloalkyl group such as a cyclopentylgroup and a cyclohexyl group; and an aromatic hydrocarbon group such asa phenyl group.

R² is preferably a C1-C6 saturated hydrocarbon group, more preferably amethyl group or an ethyl group, and still more preferably a methylgroup.

Examples of the aromatic hydrocarbon group represented by Ar include aC6-C36 arylene groups such as a phenylene group, a naphthalene group,and an anthracene group.

The aromatic hydrocarbon group has preferably 6 to 24 carbon atoms, morepreferably 6 to 18 carbon atoms.

Examples of the substituent on the aromatic hydrocarbon group include ahydroxy group, a halogen atom, a cyano group, a C1-C12 alkyl group, aC1-C12 alkoxy group, a C2-C13 alkoxycarbonyl group, a C2-C13alkylcarbonyl group, a C2-C13 alkylcarbonyloxy group, a C3-C12 alicyclichydrocarbon group, a C6-C10 aromatic hydrocarbon group, and anycombinations consisting of these groups.

Examples of a halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl groupand a dodecyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group,apropoxygroup, abutoxygroup, a pentyloxygroup, a hexyloxy group, anoctyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxygroup, an undecyloxy group, and a dodecyloxy group.

Examples of the alkoxycarbonyl group include a methoxycarbonyl group, anethoxycarbonyl group and a butoxycarbonyl group. Examples of thealkylcarbonyl group include an acetyl group, a propionyl group and abutyryl group. Examples of the alkylcarbonyloxy group include anacetyloxy group, a propionyloxy group and a butyryloxy group.

The alicyclic hydrocarbon group may be a monocyclic one or polycyclicone, examples of which include the following ones.

In each group, ** represents a binding position to an aromatichydrocarbon group.

Examples of the aromatic hydrocarbon group include a phenyl group, anaphthyl group, a tolyl group, a xylyl group, and a cyclohexylphenylgroup.

Other substituents on the aromatic hydrocarbon group include a C1-C12hydroxyalkyl group such as a hydroxymethyl group and a hydroxyethylgroup; a C2-C24 alkoxyalkoxy group such as ethoxyethoxy group; and aC7-C22 aralkyl group such as a benzyl group.

The “acid-labile group” for R³ means a group which can have a hydroxygroup resulting from removing a group represented by R³ therefrom by theaction of an acid such as p-toluenesulfonic acid.

For Resin (A), the acid-labile groups represented by formulae (1a) and(2a) are preferred.

in which R^(aa1), R^(aa2) and R^(aa3) independently each represent aC1-C8 alkyl group in which a hydrogen atom can be replaced by asubstituent, a C3-C20 alicyclic hydrocarbon group in which a hydrogenatom can be replaced by a substituent, “naa” represents an integer of 0or 1, and * represents a binding position.

in which R^(aa1′) and R^(aa2′) independently each represent a hydrogenatom or a C1-C12 hydrocarbon group, and R^(aa3′) represents a C1-C20hydrocarbon group, X^(a) represents an oxygen atom or a sulfur atom,and * represents a binding position.

For R^(aa1), R^(aa2) and R^(aa3), specific examples of the alkyl groupinclude a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group andan octyl group.

For R^(aa1), R^(aa2) and R^(aa3), the alicyclic hydrocarbon group may bemonocyclic or polycyclic. Examples of the alicyclic hydrocarbon groupinclude a monocyclic alicyclic hydrocarbon group such as a C3-C20cycloalkyl group (e.g. a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group) and a polycyclic alicyclichydrocarbon group such as a decahydronaphthyl group, an adamantyl group,a norbornyl group, and the followings:

in which * represents a binding position.

The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms.

Examples of the substituent on the alkyl group represented by R^(aa1),R^(aa2) or R^(aa3) include a C3-C20 alicyclic hydrocarbon group.Examples of the substituent on the alicyclic hydrocarbon grouprepresented by R^(aa1), R^(aa2) or R^(aa3) include a C1-C8 alkyl group.Specific examples of the alkyl or alicyclic hydrocarbon group which hasa substituent include a methylcyclohexyl group, a dimethylcyclohexylgroup, a methylnorbornyl group, a cyclohexylmethyl group, anadamantylmethyl group and a norbornylethyl group.

The “naa” is preferably 0.

The group represented by formula (1a) wherein R^(aa1), R^(aa2) andR^(aa3) independently each represent a C1-C8 alkyl group such as atert-butyl group, the group represented by formula (1a) wherein R^(aa1)and R^(aa2) are bonded to each other to form an adamantyl ring andR^(aa3) is a C1-C8 alkyl group such as a 2-alkyl-2-adamantyl group, andthe group represented by formula (1a) wherein R^(aa1) and R^(aa2) areC1-C8 alkyl groups and R^(aa3) is an adamantyl group such as a1-(1-adamantyl)-1-alkylalkoxycarbonyl group are preferred.

For formula (2a), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group anda group consisting of two or more of them.

Examples of the aliphatic hydrocarbon group and the alicyclichydrocarbon group include the same as described above. Examples of thearomatic hydrocarbon group include an aryl group such as a phenyl group,a naphthyl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, an anthryl group, a phenanthryl group,a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

In formula (2a), at least one of R^(aa1′) and R^(aa2′) is preferably ahydrogen atom.

Specific examples of the group represented by formula (1a) include thefollowings.

Specific examples of the group represented by formula (2a) include thefollowings.

In formula (I), all of the groups represented by R³ are preferably thesame as each other.

Ar is preferably a phenylene group or a naphtylene group, and morepreferably a phenylene group.

R¹ is preferably a methyl group.

R² is preferably a methyl group or an ethyl group, and more preferably amethyl group.

R³ is preferably a hydrogen atom or a C2-C4 alkoxyalkyl group, morepreferably a hydrogen atom, a methoxyethyl group or an ethoxyethylgroup, and still more preferably a hydrogen atom or an ethoxyethylgroup.

Examples of the structural unit represented by formula (I) include thefollowing ones and the structural unit represented by following formulaein which a methyl group corresponding to R¹ by formula (I) has beenreplaced by a hydrogen atom. The structural unit represented by formula(I) is represented by preferably formulae (I-1) to (I-6), and morepreferably formulae (I-1) to (I-3).

Resin (A) may have two or more kinds of the structural unit representedby the formula (I).

Resin (A) may consist of the single structural unit represented by theformula (I) or two or more kinds of the structural units represented bythe formula (I), or may further comprise another structural unit thanone represented by the formula (I).

When Resin (A) further comprises the another structural unit, the amountof the structural unit represented by the formula (I) is usually 5% to90% by mole, preferably 10% to 80% by mole, more preferably 15% to 70%by mole.

Examples of the another structural unit include other structural unitshaving an acid-labile group and being different from the structural unitrepresented by the formula (I) [which structural unit is sometimesreferred to as “the structural unit (a1)” ], and structural units havingno acid-labile group [which structural unit is sometimes referred to as“the structural unit (s)” ].

<Structural Unit (a1)>

The structural unit (a1) is derived from a compound having anacid-labile group which compound is sometimes referred to as “Monomer(a1)”.

The “acid-labile group” for the structural unit (a1) means a group whichhas a hydrophilic group, such as a hydroxy group or a carboxy group,resulting from removing a leaving group therefrom by the action of anacid.

For Resin (A), the acid-labile groups represented by formulae (1) and(2) are preferred.

In formula (1), R^(a1), R^(a2) and R^(a3) independently each represent aC1-C8 alkyl group, a C3-C20 alicyclic hydrocarbon group or a groupconsisting of them, and R^(a1) and R^(a2) can be bonded each other toform a C3-C20 alicyclic hydrocarbon group together with the carbon atomto which R^(a1) and R^(a2) are bonded, “na” and “ma” each represent aninteger of 0 or 1 provided that at least one of them represents 1, and *represents a binding position.

In formula (2), R^(a1′) and R^(a2′) independently each represent ahydrogen atom or a C1-C12 hydrocarbon group, and R^(a3′) represents aC1-C20 hydrocarbon group, and R^(a2′) and R^(a3′) can be bonded eachother to form a C3-C20 heterocyclic group together with X and the carbonatom to which R^(a2′) and R^(a3′) are bonded, and one or more —CH₂— inthe hydrocarbon group and the heterocyclic group can be replaced by —O—or —S—, X represents an oxygen atom or a sulfur atom, “na′” representsan integer of 0 or 1, and * represents a binding position. For R^(a1),R^(a2) and R^(a3), specific examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group and an octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.

Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group) and a polycyclic alicyclic hydrocarbon group such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowings:

in which * represents a binding position.

The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms.

Examples of the group consisting of alkyl and alicyclic hydrocarbongroup include a methylcyclohexyl group, a dimethylcyclohexyl group, amethylnorbornyl group, an adamantylmethyl group, and a norbornylethylgroup.

The “ma” is preferably 0. The “na” is preferably 1.

When the divalent hydrocarbon group is formed by bonding R^(a1) andR^(a2) each other, examples of the moiety —C(R^(a1)) (R^(a2)) (R^(a3))include the following groups and the divalent hydrocarbon grouppreferably has 3 to 12 carbon atoms.

wherein R^(a3) is the same as defined above and * represents a bindingposition.

For formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group anda group consisting of two or more of them.

Examples of the aliphatic hydrocarbon group and the alicyclichydrocarbon group include the same as described above. Examples of thearomatic hydrocarbon group include an aryl group such as a phenyl group,a naphthyl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, an anthryl group, a phenanthryl group,a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the heterocyclic group formed by bonding R^(a2′) and R^(a3′)together with X and the carbon atom to which R^(a2′) and R^(a3′) arebonded include the following ones.

wherein * represents a binding position.

In formula (2), at least one of R^(a1′) and R^(a2′) is preferably ahydrogen atom. The “na′” is preferably 0.

Examples of the group represented by formula (1) include the followingones:

The group represented by formula (1) wherein R^(a1), R^(a2) and R^(a3)independently each represent a C1-C8 alkyl group, ma is 0, and na is 1,such as a tert-butyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) arebonded each other to form an adamantyl ring, R^(a3) is a C1-C8 alkylgroup, ma is 0, and na is 1, such as a 2-alkyl-2-adamantyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) are C1-C8alkyl groups, R^(a3) is an adamantyl group, ma is 0, and na is 1, suchas a 1-(1-adamantyl)-1-alkylalkoxycarbonyl group. Specific examples ofthe group represented by formula (1) include the following.

Specific examples of the group represented by formula (2) include thefollowing.

Monomer (a1) is preferably a monomer having an acid-labile group in itsside chain and an ethylenic unsaturated group, more preferably a(meth)acrylate monomer having an acid-labile group in its side chain,and still more preferably a (meth)acrylate monomer having the grouprepresented by formula (1) or (2).

The (meth)acrylate monomer having an acid-labile group in its side chainis preferably those which comprise a C5-C20 alicyclic hydrocarbon group.The resin which comprises a structural unit derived from such monomerscan provide improved resolution for a photoresist pattern to be preparedtherefrom.

The structural unit derived from a (meth)acrylate monomer having thegroup represented by formula (1) is preferably one of structural unitsrepresented by formulae (a1-0), (a1-1) and (a1-2).

In each formula, L^(a01), L^(a1) and L^(a2) each independently represent—O— or *—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7and * represents a binding position to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,

R^(a02), R^(a03), R_(a04), R^(a6) and R^(a7) each independentlyrepresent a C1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, ora group formed by combining them,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

Hereinafter, the structural units represented by formulae (a1-0), (a1-1)and (a1-2) are referred to as “structural unit (a1-0)”, “structural unit(a1-1)” and “structural unit (a1-2)”, respectively. Resin (A) maycomprise two or more of such structural units.

L^(a01) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— in which * representsa binding position to —CO—, and f1 represents an integer of 1 to 4, andis more preferably *—O— or *—O—CH₂—CO—O—, and is especially preferably*—O—.

R^(a01) is preferably a methyl group.

For R^(a02), R^(a03) and R^(a04), examples of the alkyl group, thealicyclic hydrocarbon group and the group formed by combining theminclude the same as referred for R^(a1), R^(a2) and R^(a3).

The alkyl group preferably has 1 to 6 carbon atoms.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms andmore preferably 3 to 6 carbon atoms. The alicyclic hydrocarbon group ispreferably a saturated aliphatic cyclic hydrocarbon group.

The group formed by combining them preferably has 18 carbon atoms orless in total, examples of which include a methylcyclohexyl group, adimethylcyclohexyl group, and a methylnorbornyl group.

Each of R^(a02) and R^(a03) is preferably a C1-C6 alkyl group, morepreferably a methyl group and an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group and a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group, and an adamantyl group.

Each of L^(a1) and L^(a2) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— inwhich * represents a binding position to —CO—, and f1 is the same asdefined above, and is more preferably *—O— or *—O—CH₂—CO—O—, and isespecially preferably *—O—.

Each of R^(a4) and R^(a5) is preferably a methyl group.

For R^(a6) and R^(a7), examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a tert-butyl group, a pentyl group, a heptyl group, a2-ethylheptyl group and an octyl group.

For R^(a6) and R^(a7), examples of the alicyclic hydrocarbon groupinclude a monocyclic alicyclic hydrocarbon group such as a cyclohexylgroup, a methylcyclohexyl group, a dimethylcyclohexyl group, acycloheptyl group and a methylcycloheptyl group, and a polycyclicalicyclic hydrocarbon group such as a decahydronaphthyl group, anadamantyl group, a norbornyl group, and a methylnorbornyl group.

For R^(a6) and R^(a7), examples of the group consisting of an alkylgroup and an alicyclic hydrocarbon group include an aralkyl group suchas a benzyl group, and a phenethyl group.

The alkyl group represented by R^(a6) and R^(a7) is preferably a C1-C6alkyl group, more preferably a methyl group, an ethyl group or anisopropyl group, and still more preferably an ethyl group, or anisopropyl group.

The alicyclic hydrocarbon group represented by R^(a6) and R^(a7) ispreferably a C3-C8 alicyclic hydrocarbon group, more preferably a C3-C6alicyclic hydrocarbon group.

The “m1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1′” is preferably 0 or 1.

Examples of the structural unit (a1-0) include those represented byformulae (a1-0-1) to (a1-0-12), preferably those represented by formulae(a1-0-1) to (a1-0-10).

Examples of the structural unit (a1-0) further include such groups thata methyl group has been replaced by a hydrogen atom in any one offormulae (a1-0-1) to (a1-0-12).

Examples of the monomer from which the structural unit (a1-1) is derivedinclude the monomers described in JP2010-204646A1, and the followingmonomers represented by the formulae (a1-1-1) to (a1-1-4) and suchgroups that a methyl group has been replaced by a hydrogen atom in anyone of formulae (a1-1-1) to (a1-1-4), preferably the following monomersrepresented by the formulae (a1-1-1) to (a1-1-4).

Preferred examples of the structural unit (a1-2) include onesrepresented by formulae (a1-2-1) to (a1-2-6) and those represented bythe formulae in which a methyl group corresponding to R^(a5) has beenreplaced by a hydrogen atom, more preferably the monomers represented byformulae (a1-2-2), (a1-2-5) and (a1-2-6).

When the resin comprises one or more of the structural units representedby formulae (a1-0), (a1-1) and (a1-2), the total content of thestructural units is usually 10 to 95% by mole, preferably 15 to 70% bymole and more preferably 15 to 65% by mole, still more preferably 20 to60% by mole, and further more preferably 20 to 55% by mole, based on100% by mole of all the structural units of the resin.

Examples of the structural unit (a1) having the group represented byformula (2) include a structural unit represented by formula (a1-4). Thestructural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^(a32) represents a hydrogen atom, a halogen atom or aC1-C6 alkyl group that may have a halogen atom,

R^(a33) in each occurrence independently represent a halogen atom, ahydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acylgroup, a C2-C4 acyloxy group, an acryloyloxy group or methacryloyloxygroup,

“1a” represents an integer 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group; and

R^(a36) represents a C1-C20 hydrocarbon group, or R^(a35) and R^(a36)may be bonded together with a C—O bonded thereto to form a divalentC3-C20 heterocyclic group, and a methylene group contained in thehydrocarbon group or the divalent heterocyclic group may be replaced byan oxygen atom or a sulfur atom.

Examples of the alkyl group of R^(a32) and R^(a33) include methyl,ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkylgroup is preferably a C1-C4 alkyl group, and more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom of R^(a32) and R^(a33) include a fluorine,chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom includetrifluoromethyl, difluoromethyl, methyl, perfluoroethyl,1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl,1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl,1,1,1,2,2,3,3,4,4-nonafluoropentyl, n-pentyl, n-hexyl andn-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy and hexyloxy groups. The alkoxy group is preferably a C1-C4alkoxy group, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group.

Examples of the acyl group include acetyl, propionyl and butyryl groups.Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups. Examples of the hydrocarbon group for R^(a34) andR^(a35) are the same examples as described in R^(a1′) to R^(a2′) in theformula (2).

Examples of hydrocarbon group for R^(a36) include a C1-C18 alkyl group,a C3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbongroup or a group formed by combining thereof.

In the formula (a1-4), R^(a32) is preferably a hydrogen atom.

R^(a33) is preferably a C1-C4 alkoxy group, more preferably a methoxygroup or an ethoxy group, and still more preferably a methoxy group.“1a” is preferably 0 or 1, and more preferably 0. R^(a34) is preferablya hydrogen atom. R^(a35) is preferably a C1-C12 hydrocarbon group, andmore preferably a methyl group or an ethyl group.

The hydrocarbon group for R^(a36) is preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a combination thereof, and more preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group or a C7-C18 aralkyl group. The alkylgroup and the alicyclic hydrocarbon group for R^(a36) are preferablyunsubstituted. When the aromatic hydrocarbon group of R^(a36) has asubstituent, the substituent is preferably a C6-C10 aryloxy group.

Examples of the structural unit (a1-4) include those derived from themonomers described in JP2010-204646A1. Among them, the structural unitis preferably the following ones represented by formula (a1-4-1) toformula (a1-4-8), and more preferably the structural units representedby formula (a1-4-1) to formula (a1-4-5).

When the resin (A) has the structural unit (a1-4), the proportionthereof is preferably 5% by mole to 60% by mole, more preferably 5% bymole to 50% by mole, and still more preferably 10% by mole to 40% bymole, based on the all the structural units of the resin (A) (100% bymole).

Examples of the structural unit having an acid-labile group representedby formula (2) include one represented by formula (a1-5).

In formula (a1-5), R^(a8) represents a hydrogen atom, a halogen atom, ora C1-C6 alkyl group which may have a halogen atom,

Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO— L⁵⁴-in which h3represents an integer of 1 to 4 and * represents a binding position toL⁵¹, L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent an oxygen atomor a sulfur atom, and

s1 represents an integer of 1 to 3, and s1′ represents an integer of 0to 3.

Herein, the structural unit representedbyformula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

Examples of halogen atoms include a fluorine atom and chlorine atom,preferably a fluorine atom.

Examples of the alkyl group which may have a halogen atom include amethyl group, an ethyl group, n-propyl group, an isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, afluoromethyl group, and a trifluoromethyl group.

In the formula (a1-5), R^(a8) preferably represents a hydrogen atom, amethyl group, or a trifluoromethyl group.

L⁵¹ represents preferably an oxygen atom.

It is preferred that one of L⁵² and L⁵³ represents an oxygen atom, whilethe other represents a sulfur atom.

s1 preferably represents 1. s1′ represents an integer of 0 to 2. Z^(a1)preferably represents a single bond or *—CH₂—CO—O— wherein * representsa binding position to L⁵¹.

Examples of the structural unit (a1-5) include one derived from monomermentioned in JP2010-61117A1, which preferably include the followingones.

Among them, the structural units represented by the formula (a1-5-1) and(a1-5-2) are more preferred.

When Resin (A) has a structural unit (a1-5), its content is usually 1 to50% by mole, preferably 3 to 45% by mole and more preferably 5 to 40% bymole, and still more preferably 5 to 30% by mole, based on 100% by moleof all the structural units of the resin.

Another example of the structural unit (a1) includes one represented byformula (a1-0X) which is sometimes referred to as “the structural unit(a1-0X)”.

In the formula, R^(x1) represents a hydrogen atom, a methyl group or anethyl group,

R^(x2) and R^(x3) each independently represent a C1-C6 saturatedhydrocarbon group, and

Ar^(x1) represents a C6-C36 aromatic hydrocarbon group.

Resin (A) may comprise two or more of such structural units. For R^(x2)and R^(x3), examples of the saturated hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group and a group formed by combiningthem.

Examples of the alkyl group include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group,a tert-butyl group, a pentyl group and a hexyl group. The alicyclichydrocarbon group may be monocyclic or polycyclic, and examples of themonocyclic alicyclic hydrocarbon group include a cyclopropyl group, acyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

For Ar^(x1), examples of the aromatic hydrocarbon group include a C6-C36aryl group such as a phenyl group, a naphthyl group and an anthrylgroup.

The aromatic hydrocarbon group has preferably 6 to 24 carbon atoms, morepreferably 6 to 18 carbon atoms, and still more preferably a phenylgroup.

Ar^(x1) is preferably a C6-C36 aromatic hydrocarbon group, morepreferably a phenyl group or a naphthyl group, and still more preferablya phenyl group.

Preferably, R^(x1), R^(X2) and R^(x3) are each independently a methylgroup or an ethyl group. More preferably, R^(x1), R^(X2) and R^(x3) area methyl group.

Examples of the structural unit (a1-0X) include the following ones andthose represented by the following formulae in which a methyl grouprepresented by R^(x1) has been replaced by a hydrogen atom, and morepreferably the structural units represented by formula (a1-0X-1) toformula (a1-0X-3).

When Resin (A) has a structural unit (a1-0X), its content is usually 5to 60% by mole, preferably 5 to 50% by mole, and more preferably 10 to40% by mole, based on 100% by mole of all the structural units of theresin.

Another example of the structural unit (a1) further includes thefollowing ones.

When Resin (A) has any one of these structural units, its content isusually 5 to 60% by mole, preferably 5 to 50% by mole, more preferably10 to 40% by mole, based on 100% by mole of all the structural units ofthe resin.

Preferably Resin (A) further comprises the structural unit (a1), andmore preferably Resin (A) further comprises at least one of thestructural units (a1-1) and (a1-2).

The structural unit (s) is derived from a monomer having no acid-labilegroup.

The structural unit (s) preferably has a hydroxy group or a lactonering.

Hereinafter, the structural unit (s) having a hydroxy group is referredto as “structural unit (a2)”, and the structural unit (s) having alactone ring is referred to as “structural unit (a3)”.

The hydroxy group which the structural unit (a2) has may be an alcoholichydroxy group or a phenolic hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, the resin which comprises the structural unit(a2) having a phenolic hydroxy group is preferred. When ArF excimerlaser (wavelength: 193 nm) is used as an exposure system, the resinwhich comprises the structural unit (a2) having an alcoholic hydroxygroup is preferred and the resin which comprises the structural unit(a2-1) described later is more preferred.

Resin (A) may have two or more of the structural units (a2). Examples ofthe structural unit (a2) having a phenolic hydroxy group include onerepresented by formula (a2-A):

In formula (a2-A), R^(a50) represents a hydrogen atom, a halogen atom, aC1-C6 alkyl group or a C1-C6 halogenated alkyl group, A^(a)50 representsa single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—, where * represents abinding position to the carbon atom bonded to R^(a51), A^(a52)represents a C1-C6 alkanediyl group, X^(a15) and X^(a52) represents —O—,—CO—O—, or —O—CO—, and nb represents an integer of 0 or 1, R^(a51) isindependently in each occurrence a halogen atom, a C1-C6 alkyl group, aC1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a methacryloyl group, and mb represents an integer of0 to 4. In the formula (a2-A), examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom or iodine atom, examplesof the C1-C6 alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, an isobutyl group, asec-butyl group, a tert-butyl group, a pentyl group and a hexyl group,and a C1-C4 alkyl group is preferred and a C1-C2 alkyl group is morepreferred and a methyl group is especially preferred.

Examples of the C1-C6 halogenated alkyl group include a trifluoromethylgroup, a pentafluoroethyl group, a heptafluoropropyl group, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group, and a C1-C4 alkoxy group is preferred and aC1-C2 alkoxy group is more preferred and a methoxy group is especiallypreferred.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group, and examples of the C2-C4 acyloxy groupinclude an acetyloxy group, a propionyloxy group and a butyryloxy group.

R^(a51) is preferably a methyl group.

R^(a50) is preferably a hydrogen atom and a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group and an ethyl group, and stillmore preferably a hydrogen atom and a methyl group.

As to A^(a50), examples of *—X^(a51)-(A^(a52)-X^(a52))^(nb)— include*—O—, *—CO—O—, *—O—CO—, *—CO—O-A^(a52)-CO—O—, *—O—CO-A^(a52)-O—,*—O-A^(a52)-CO—O—, *—CO—O-A^(a52)-O—CO—, *—O—CO-A^(a52)-O—CO—,preferably *—CO—O—, *—CO—O-A^(a52)-CO—O— and *—O-A^(a52)-CO—O—.

As to A^(a52), examples of the alkanediyl group include an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-O—CO—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—O—CO—, and stillmore preferably a single bond or *—CO—O—.

In the formula (a2-A), mb is preferably 0, 1 or 2, and is morepreferably 0 or 1, and especially preferably 0.

In formula (a2-A), a hydroxyl group on the phenyl group is positionedpreferably on o-position or p-position, and more preferably onp-position.

Examples of the structural unit (a2) include those derived from themonomers described in JP2010-204634A1 and JP2012-12577A1.

Preferred examples of the structural unit (a2) include the structuralunits represented by formulae (a2-2-1) to (a2-2-4) and those representedby formulae in which a methyl group corresponding to R^(a50) has beenreplaced by a hydrogen atom.

Among them, the structural units represented by formulae (a2-2-1) and(a2-2-3) and those represented by formulae in which a methyl groupcorresponding to R^(a)50 has been replaced by a hydrogen atom are morepreferred.

When Resin (A) has the structural unit represented by formula (a2-A),its content is usually 5 to 95% by mole and preferably 10 to 80% bymole, more preferably 15 to 80% by mole, still more preferably 10 to 70%by mole, further more preferably 15 to 65% by mole, and still furthermore preferably 20 to 65% by mole, based on the sum of the structuralunits of the resin.

Resin (A) which further comprises the structural unit represented byformula (a2-A) can be prepared, for example, by reacting, with an acid,Resin (A) which further comprises the structural unit represented byformula (a1-4), or by polymerizing Resin (A) using acetoxystyrene andfurther reacting with an alkali such as tetramethylammonium hydroxide.

Examples of the structural unit (a2) having an alcoholic hydroxy groupinclude one represented by formula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents *—O— or *—O— (CH₂)_(k2)—CO—O— inwhich * represents a binding position to —CO—, and k2 represents aninteger of 1 to 7, and o1 represents an integer of 0 to 10.

Hereinafter, the structural unit represented by formula (a2-1) isreferred to as “structural unit (a2-1)”.

In the formula (a2-1), R^(a14) is preferably a methyl group. R^(a15) ispreferably a hydrogen atom. R_(a16) is preferably a hydrogen atom or ahydroxy group. L^(a3) is preferably *—O— or *—O—(CH₂)_(f2)—CO—O— inwhich * represents a binding position to —CO—, and f2 represents aninteger of 1 to 4, is more preferably *—O— and *—O—CH₂—CO—O—, and isstill more preferably *—O—, and o1 is preferably 0, 1, 2 or 3 and ismore preferably 0 or 1.

Examples of monomers from which the structural unit (a2-1) is derivedinclude compounds as mentioned in JP2010-204646A.

Preferred examples of the structural unit (a2-1) include thoserepresented by formulae (a2-1-1) to (a2-1-6).

Among them, more preferred are the structural units represented byformulae (a2-1-1), (a2-1-2), (a2-1-3) and (a2-1-4), still more preferredare the structural units represented by formulae (a2-1-1) and (a2-1-3).

When Resin (A) has the structural unit (a2-1), its content is usually 1to 45% by mole, preferably 1 to 40% by mole, and more preferably 1 to35% by mole, still more preferably 2 to 20% by mole, further still morepreferably 2 to 10% by mole, based on the sum of the structural units ofthe resin.

Examples of the lactone ring for the structural unit (a3) include amonocyclic lactone ring such as β-propiolactone ring, γ-butyrolactonering and γ-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring. Among them, preferred areγ-butyrolactone ring and a condensed lactone ring formed fromγ-butyrolactone ring and the other ring. Preferred examples of thestructural unit (a3) include those represented by formulae (a3-1),(a3-2), (a3-3) and (a3-4).

In formulae, L^(a4), Las and L^(a6) each independently represent *—O— or*—O—(CH₂)_(k3)—CO—O— in which * represents a binding position to acarbonyl group and k3 represents an integer of 1 to 7,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a21) represents a C1-C4 monovalent aliphatic hydrocarbon group,R^(a24) represents a hydrogen atom, a halogen atom, or a C1-C6 alkylgroup which may have a halogen atom,

R^(a22), R^(a23) and R^(a2)5 each independently represent a carboxylgroup, a cyano group, or a C1-C4 aliphatic hydrocarbon group,

L^(a7) represents an oxygen atom, *¹—O-L^(a9)-O—, *¹—O-L^(a8)-CO—O—,*¹—O-L^(a8)-CO—O-L^(a9)-CO—O— or *¹—O-L^(a8)-CO—O-L^(a9)-O— in whichL^(a8) and L^(a9) each independently represent C1-C6 divalent alkanediylgroup, *¹ represents a binding position to a carbonyl group,

p1 represents an integer of 0 to 5,

q1 and r1 each independently represent an integer of 0 to 3, and

w1 represents an integer of 0 to 8.

Examples of the aliphatic hydrocarbon group represented by R^(a21),R^(a22), R^(a23) and R^(a25) include alkyl groups such as a methylgroup, an ethyl group, a propyl group, or a butyl group.

Examples of the alkyl group represented by R^(a24) include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group,and a hexyl group, preferably a C1-C4 alkyl group, and more preferably amethyl group and an ethyl group.

Examples of halogen atom represented by R^(a24) include a fluorine atom,a chlorine atom, a bromine atom and an iodine atom.

As to R^(a24), examples of the alkyl group which has an halogen atominclude a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a heptafluoroisopropyl group, a nonafluorobutylgroup, a nonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group, a perfluorohexyl group, a trichloromethyl group,a tribromomethyl group, and a triiodomethyl group.

As to L^(a8) and L^(a9), examples of the alkanediyl group include amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diylgroup, a butane-1,3-diyl group, 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Preferably, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(d1)—CO—O— in which * represents a binding position to —CO—and d1 represents an integer of 1 to 4. More preferably, L^(a4), L^(a5)and L^(a6) are *—O— and *—O—CH₂—CO—O—, and still more preferably L^(a4),L^(a5) and L^(a6) are *—O—.

R^(a18), R^(a19) and R^(a20) are preferably methyl groups. R^(a21) ispreferably a methyl group. Preferably, R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or amethyl group. Preferably, p1, q1 and r1 each independently represent aninteger of 0 to 2, and more preferably p1, q1 and r1 each independentlyrepresent 0 or 1.

R^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably an oxygen atom or *¹—O-L^(a8)-CO—O—, morepreferably an oxygen atom, *¹—O—CH₂—CO—O— or *¹—O—C₂H₄—CO—O—.

The formula (a3-4)′ is preferably the following one.

In the formula, R^(a24) and L^(a7) are as defined above, respectively.Examples of the monomer from which the structural unit (a3) is derivedinclude those mentioned in US2010/203446A1, US2002/098441A1 andUS2013/143157A1.

Examples of the structural unit (a3) include the following ones.

Other examples of the structural unit (a3) include those represented byformulae (a3-1) to (a3-4) in which the methyl group corresponding toR^(a18), R^(a19), R^(a20) and R^(a24) Of formulae (a3-1) to (a3-4) hasbeen replaced by a hydrogen atom.

When Resin (A) has the structural unit (a3), its content thereof ispreferably 5 to 70% by mole, and more preferably 10 to 65% by mole andmore preferably 10 to 60% by mole, based on the sum of the structuralunits of the resin.

When Resin (A) has the structural unit (a3-1), (a3-2), (a3-3) or (a3-4),its content thereof is preferably 5 to 60% by mole, and more preferably5 to 50% by mole and more preferably 10 to 50% by mole, based on the sumof the structural units of the resin.

Other examples of the structural unit (s) include a structural unithaving a fluorine atom and a structural unit which has a hydrocarbon notbeing removed therefrom by action of an acid. Hereinafter, thestructural unit (s) havingahalogenatomis referred to as “structural unit(a4)”.

Halogen atoms for the structural unit (a4) may be a fluorine atom, achlorine atom, a bromine atom, or an iodine atom. The structural unit(a4) has preferably a fluorine atom.

Examples of the structural unit (a4) include the following one.

In the formula, R⁴¹ represents a hydrogen atom or a methyl group, R⁴²represents a C1-C24 saturated hydrocarbon group having a fluorine atomin which hydrocarbon group a methylene group can be replaced by anoxygen atom or a carbonyl group.

Examples of the saturated hydrocarbon group include C1-C24 chainhydrocarbon group, an alicyclic hydrocarbon group including a monocyclicor polycyclic hydrocarbon group, and any combinations of these groups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group,decahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups:

Examples of the combinations of these groups include any combination ofan alkyl or alkanediyl group with an alicyclic hydrocarbon group, whichspecifically include-[alkanediyl group]-[alicyclic hydrocarbon group],-[alicyclic hydrocarbon group]-[alkyl group] and -[alkanediylgroup]-[alicyclic hydrocarbon group]-[alkyl group].

Typical examples of the structural unit (a4) include structural unitsrepresented by formulae (a4-0), (a4-1) and (a4-4).

In the formula (a4-0), R^(5a) represents a hydrogen atom or a methylgroup, L^(4a) represents a single bond or a C1-C4 alkanediyl group,L^(3a) represents a C1-C8 perfluoroalkanediyl group, or a C3-C12perfluorocycloalkanediyl group, and R^(6a) represents a hydrogen atom ora fluorine atom.

For L^(4a), examples of the alkanediyl group include a linear alkanediylgroup such as a methylene group, an ethylene group, a propane-1,3-diylgroup, and butane-1,4-diyl group, and a branched alkanediyl group suchas an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diylgroup, a 2-methylpropane-1,3-diyl group and 2-methylpropane-1,2-diylgroup.

Examples of the perfluoroalkanediyl group for L^(3a) includedifluoromethylene, perfluoroethylene, perfluoropropane-1,3-diyl,perfluoropropane-1,2-diyl, perfluoropropane-2,2-diyl,perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl,perfluorobutane-1,2-diyl, perfluoropentane-1,5-diyl,perfluoropentane-2,2-diyl, perfluoropentane-3,3-diyl,perfluorohexane-1,6-diyl, perfluorohexane-2,2-diyl,perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl,perfluoroheptane-2,2-diyl, perfluoroheptane-3,4-diyl,perfluoroheptane-4,4-diyl, perfluorooctan-1,8-diyl,perfluorooctane-2,2-diyl, perfluorooctan-3,3-diyl andperfluorooctane-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L^(3a) includeperfluorocyclohexanediyl, perfluorocyclopentanediyl,perfluorocycloheptanediyl and perfluoroadamantanediyl groups. L^(3a) ispreferably a C1-C6 perfluoroalkanediyl group, more preferably a C1-C3perfluoroalkanediyl group.

L^(4a) is preferably a single bond, a methylene group or an ethylenegroup, more preferably a single bond or a methylene group. Examples ofthe structural unit represented by formula (a4-0) include the structuralunits represented by the following formulae and those represented by thefollowing formulae in which a methyl group has been replaced by ahydrogen atom.

The structural unit represented by formula (a4-1) is as follows.

In the formula, R^(a41) represents a hydrogen atom or a methyl group;R^(a42) represents a C1-C20 saturated hydrocarbon group which may have asubstituent and in which a methylene group can be replaced by an oxygenatom or a carbonyl group, provided that each or both of A^(a41) andR^(a42) have a fluorine atom; and

A^(a41) represents a C1-C6 alkanediyl group which may have a substituentor a moiety represented by formula (a-g1):

in which s represents an integer of 0 to 1,

A^(a42) and A^(a44) respectively represent a C1-C5 saturated hydrocarbongroup which may have a substituent,

A^(a43) represents a single bond or a C1-C5 chain or alicyclichydrocarbon group which may have a substituent,

X^(a41) and X^(a42) respectively represent —O—, —CO—, —CO—O—, or —O—CO—,provided that the sum of carbon atoms of A^(a42), A^(a43), A^(a44),X^(a41) and X^(a42) are each 7 or less; and

A^(a44) is bonded to —O—CO—R^(a42).

The saturated hydrocarbon group for R^(a42) includes a chain saturatedhydrocarbon group, an alicyclic hydrocarbon group including a monocyclichydrocarbon group and a polycyclic hydrocarbon group, and anycombination of these hydrocarbon groups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a hexadecyl group, a pentadecyl group, a hexyldecyl group, aheptadecyl group and an octadecyl group.

Examples of alicyclic hydrocarbon groups include cycloalkyl groups suchas a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group; and monovalent polycyclic hydrocarbon groups such as adecahyrdonaphthyl group, an adamantyl group, a norbornyl group, and thefollowing groups where * represents a binding position.

Examples of the combination of these groups include combination of analkanediyl or alkyl group with an alicyclic hydrocarbon group such as-[alkanediyl group]-[alicyclic hydrocarbon group], -[alicyclichydrocarbon group]-[alkyl group], and -[alkanediyl group]-[alicyclichydrocarbon group]-[alkyl group]. The hydrocarbon group represented byR^(a42) preferably has a substituent.

Examples of the substituent include a halogen atom and a grouprepresented by formula (a-g3):

—X^(a43)-A^(a45)  (a-g3)

in which X^(a43) represents an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group, and

A^(a45) represents a C1-C17 chain or alicyclic hydrocarbon group whichmay have a fluorine atom.

Examples of the chain or alicyclic hydrocarbon group for A^(a45) includealkyl groups such as a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a heptyl group, an octylgroup, a decyl group, a dodecyl group, a hexadecyl group, a pentadecylgroup, a hexyldecyl group, a heptadecyl group and an octadecyl group;

monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andmonovalent polycyclic hydrocarbon groups such as a decahyrdonaphthylgroup, an adamantyl group, a norbornyl group, and the following groupswhere * represents a binding position.

R^(a42) is preferably a chain or alicyclic hydrocarbon group which mayhave a halogen atom, more preferably an alkyl group which has a halogenatom or a group represented by formula (a-g3).

If R^(a42) is a chain or alicyclic hydrocarbon group which has a halogenatom, it is preferably a chain or alicyclic hydrocarbon group which hasa fluorine atom, more preferably a perfluoroalkyl group or aperfluorocycloalkyl group, and still more preferably a C1-C6, especiallyC1-C3, perfluoroalkyl group.

Specific examples of the perfluoroalkyl group include a perfluoromethylgroup, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutylgroup, a perfluoropentyl group, a perfluorohexyl group, aperfluoroheptyl group, and a perfluorooctyl group. Specific examples ofthe perfluorocycloalkyl group include a perfluorocyclohexyl group.

Examples of the substituents for R^(a42) include a hydroxy group, aC1-C6 alkoxy group, and a halogen atom such as fluorine atom. If R^(a42)is a chain or alicyclic hydrocarbon group which has a group representedby formula (a-g3), R^(a42) has preferably 15 or less carbon atoms, morepreferably 12 or less carbon atoms.

If R^(a42) has a group represented by formula (a-g3), R^(a42) haspreferably one group represented by formula (a-g3).

The chain or alicyclic hydrocarbon group which has a group representedby formula (a-g3) is preferably a group represented by formula (a-g2):

-A^(a46)-X^(a44)-A^(a47)  (a-g2)

in which A^(a46) represents a C1-C17 chain or alicyclic hydrocarbongroup which may have a fluorine atom, X^(a44) represents a carbonyloxygroup or an oxycarbonyl group, and A^(a47) represents a C1-C17 chain oralicyclic hydrocarbon group which may have a fluorine atom, providedthat A^(a46), A^(a47) and X^(a44) have 18 or less of carbon atoms intotal and one or both of A^(a46) and A^(a47) have a fluorine atom. Thechain or alicyclic hydrocarbon group represented by A^(a46) haspreferably 1 to 6, more preferably 1 to 3 carbon atoms. The chain oralicyclic hydrocarbon group represented by A^(a47) has preferably 4 to15, more preferably 5 to 12 carbon atoms. A^(a47) is more preferably acyclohexyl group or an adamantyl group. Examples of the moietyrepresented by -A^(a46)-X^(a44)-A^(a47) include the following ones.

In each formula, * represents a binding position to a carboxy group.Examples of A^(a41) typically include a C1-C6 alkanediyl group which maybe a linear chain or branched chain. Specific examples of them includelinear chain alkanediyl groups such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, or a hexane-1,6-diyl group; and branched chainalkanediyl groups such as a propane-1,3-diyl group, a butane-1,3-diylgroup, a 1-methylbutane-1,2-diyl group, or a 2-methylbutane-1,4-diylgroup. Examples of the substituents on the alkanediyl group include ahydroxy group or a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably an ethylene group. Examplesof the alkanediyl group represented by A^(a42), A^(a43) and A^(a44)include a methylene group, an ethylene group, a propane-1,3-diyl group,a butane-1,4-diyl group, a 2-methylpropane-1,3-diyl group, or a2-methylbutane-1,4-diyl group. Examples of the substituents on thealkanediyl group include a hydroxy group or a C1-C6 alkoxy group.

X^(a42) represents an oxygen atom, a carbonyl group, a carbonyloxy groupor an oxycarbonyl group.

Examples of the moiety represented by formula (a-g1) where X^(a42) is anoxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonylgroup include the following ones:

in which * and ** represent binding positions, and * represents abinding position to —O—CO—R^(a42).

Typical examples of the structural unit represented by formula (a4-1)include the structural units represented by the following formulae andthose represented by the following formulae in which a methyl groupcorresponding to R^(a41) has been replaced by a hydrogen atom.

The structural unit represented by the formula (a4-1) is typically astructural unit represented by formula (a4-2):

wherein R^(f5) represents a hydrogen atom or a methyl group, L⁴⁴represent a C1-C18 alkanediyl group in which a methylene group can bereplaced by —O— or —CO—, and

R^(f6) represents a C1-C20 saturated hydrocarbon group that has afluorine atom, provided that L⁴⁴ and R^(f6) have 2 to 21 carbon atoms intotal.

Examples of the divalent saturated hydrocarbon group for L⁴⁴ include alinear alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diylgroups; and a branched alkanediyl group such as1-methylpropane-1,3-diyl, 2-methylpropane-, 3-diyl,2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl and2-methylbutane-1,4-diyl groups. Examples of the saturated hydrocarbongroup for R^(f6) include an aliphatic hydrocarbon group and an aromatichydrocarbon group. The aliphatic hydrocarbon group includes chain andcyclic groups, and a combination thereof. The aliphatic hydrocarbongroup is preferably an alkyl group and a cyclic aliphatic hydrocarbongroup. Examples of the alkyl group include methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl,n-octyl and 2-ethylhexyl groups.

Examples of the cyclic aliphatic hydrocarbon group include any of amonocyclic group and a polycyclic group. Examples of the monocyclicalicyclic hydrocarbon group include a cycloalkyl group such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups.Examples of the polycyclic hydrocarbon groups include decahydronaphthyl,adamantyl, 2-alkyladamantane-2-yl, 1-(adamantane-1-yl)alkane-1-yl,norbornyl, methylnorbornyl and isobornyl groups.

Examples of the saturated hydrocarbon group having a fluorine atom forR^(f6) include an alkyl group having a fluorine atom and an alicyclichydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include afluorinated alkyl group such as difluoromethyl, trifluoromethyl,1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl,perfluoropropyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodeca fluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

In the formula (a4-2), L⁴⁴ is preferably a C2-C4 alkanediyl group, andmore preferably an ethylene group.

R^(f6) is preferably a C1-C6 fluorinated alkyl group.

Examples of the structural unit represented by formula (a4-2) includeones represented by the formulae (a4-1-1) to (a4-1-11) and those inwhich a methyl group corresponding to R^(f5) has been replaced by ahydrogen atom.

Another typical example of the structural unit represented by theformula (a4-1) includes one represented by formula (a4-3).

In formula, R^(f7) represents a hydrogen atom or a methyl group. L⁵represents a C1-C6 alkanediyl group.

A^(f13) represents a C1-C18 saturated hydrocarbon group which may have afluorine atom.

X^(f12) represents a carbonyloxy group or an oxycarbonyl group.

A^(f14) represents a C1-C17 saturated hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing aliphatic hydrocarbon group.

Examples of the alkanediyl group for L⁵ include the same ones as thosefor L^(4a).

A^(f13) further includes combined groups of chain hydrocarbon groups andalicyclic hydrocarbon groups.

As to A^(f13), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a divalent saturated chain hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkanediylgroup.

Examples of the divalent chain saturated hydrocarbon group which mayhave a fluorine atom include an alkanediyl group such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group andpentanediyl group; and a perfluoroalkanediyl group such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group andperfluoropentanediyl group.

The divalent cyclic saturated hydrocarbon group which may have afluorine atom may be a divalent monocyclic or polycyclic group. Examplesof the divalent monocyclic hydrocarbon group which may have a fluorineatom include a cyclohexanediyl group and a perfluorocyclohexanediylgroup.

Examples of the divalent polycyclic hydrocarbon group which may have afluorine atom include an adamantanediyl group, norbornanediyl group, anda perfluoroadamantanediyl group.

In the group represented by A^(f4), the aliphatic hydrocarbon groupincludes chain saturated hydrocarbon groups, cyclic saturatedhydrocarbon groups and combined groups of these saturated hydrocarbongroups.

As to A^(f4), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a saturated aliphatic hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkyl group.

Examples of the chain hydrocarbon group which may have a fluorine atominclude a trifluoromethyl group, a fluoromethyl group, a methyl group, aperfluoroethyl group, a 1,1,1-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 1,1,1,2,2-pentafluoropropyl group, a propyl group, a perfluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, 1,1,1,2,2,3,3,4,4-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, aperfluoroheptyl group, an octyl group and a perfluorooctyl group.

The alicyclic hydrocarbon group which may have a fluorine atom may bemonocyclic or polycyclic group.

Examples of the monovalent monocyclic hydrocarbon group which may have afluorine atom include a cyclopropyl group, a cyclopentyl group, acyclohexyl group, and a perfluorocyclohexyl group.

Examples of the polycyclic hydrocarbon group which may have a fluorineatom include an adamantyl group, a norbornyl group, and aperfluoroadamantyl group.

Examples of the combined groups of the above-mentioned chain andalicyclic hydrocarbon groups include a cyclopropylmethyl group, acyclobutylmethyl group, an adamantylmethyl group, a norbornylmethylgroup and a perfluoroadamantylmethyl group. In formula (a4-3), L⁵ ispreferably an ethylene group. The chain or alicyclic hydrocarbon grouprepresented by A^(f13) has preferably 6 or less, more preferably 2 to 3,carbon atoms. The chain or alicyclic hydrocarbon group represented byA^(f14) has preferably 3 to 12, more preferably 3 to 10, carbon atoms.A^(f14) has preferably a C3-C12 alicyclic hydrocarbon group, morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group or an adamantyl group. Examples of thestructural unit represented by formula (a4-3) include preferably thoserepresented by the he formulae (a4-1′-1) to (a4-1′-11) and those inwhich a methyl group corresponding to R^(f7) has been replaced by ahydrogen atom.

Another example of the structural unit (a4) includes those representedby formula (a4-4).

In formula (a4-4), R^(f21) represents a hydrogen atom or a methyl group;A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O— (CH₂)_(j3)— or—(CH₂)_(j4)—CO—O— (CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; and

R^(f22) represents a C1-C10 hydrocarbon group having a fluorine atom.R^(f22) is preferably a C1-C10 alkyl group having a fluorine atom or aC3-C10 alicyclic hydrocarbon group having a fluorine atom, morepreferably a C1-C10 alkyl group having a fluorine atom, and still morepreferably a C1-C6 alkyl group having a fluorine atom. In formula(a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferably a methyleneor ethylene group, and still more preferably a methylene group.

Examples of the structural unit represented by formula (a4-4) includepreferably the following ones and those represented by the followingformulae in which the methyl group corresponding to R^(f21) has beenreplaced by a hydrogen atom.

When Resin (A) has the structural unit (a4), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole and still morepreferably 3 to 10% by mole based on 100% by mole of all the structuralunits of the resin.

Other examples of the structural unit (s) include one having anacid-stable hydrocarbon group. The structural unit (s) having anacid-stable hydrocarbon group is sometimes referred to as “structuralunit (a5)”.

Herein, the term “acid-stable hydrocarbon group” means such ahydrocarbon group that is not removed from the structural unit havingthe group by action of an acid generated from an acid generator asdescribed above.

The acid-stable hydrocarbon group may be a linear, branched or cyclichydrocarbon group.

The structural unit which has a hydrocarbon not being removed therefromby action of an acid may have a linear, branched or cyclic hydrocarbon,preferably an alicyclic hydrocarbon group.

Examples of the structural unit having an acid-stable hydrocarbon groupinclude one represented by formula (a5-1):

where R⁵¹ represents a hydrogen atom or a methyl group;

R⁵² represents a C3-C18 monovalent alicyclic hydrocarbon group which mayhave a C1-C8 monovalent aliphatic hydrocarbon group as a substituent,provided that the alicyclic hydrocarbon group has no substituent on thecarbon atom bonded to L⁵⁵; and

L⁵⁵ represents a single bond or a C1-C18 divalent saturated hydrocarbongroup where a methylene group can be replaced by an oxygen atom orcarbonyl group.

The alicyclic hydrocarbon group represented by R⁵² may be a monocyclicor a polycyclic one.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon group such as a C3-C18 cycloalkyl group (e.g. a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group) anda polycyclic alicyclic hydrocarbon group such as an adamantyl group, ora norbornyl group.

Examples of the aliphatic hydrocarbon group include an alkyl groupe suchas a methyl group, an ethyl group, n-propyl group, isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, an octyl group and 2-ethylhexyl group. Examples of thealicyclic hydrocarbon group having a substituent include a3-hydroxyadamantyl group, and a 3-methyladamantyl group. R⁵² ispreferably a C3-C18 unsubstituted alicyclic hydrocarbon group, morepreferably an adamantyl group, a norbornyl group or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group represented by L⁵⁵include divalent aliphatic hydrocarbon groups and divalent alicyclichydrocarbon groups, preferably divalent aliphatic hydrocarbon groups.

Examples of divalent aliphatic hydrocarbon groups include alkanediylgroups such as a methylene group, an ethylene group, a propanediylgroup, a butanediyl group and a pentanediyl group. The divalentalicyclic hydrocarbon groups may be monocyclic or polycyclic one.

Examples of divalent monocyclic hydrocarbon groups includecycloalkanediyl groups such as a cyclopentanediyl group and acyclohexanediyl group. Examples of divalent polycyclic alicyclichydrocarbon groups include an adamantanediyl group and a norbornanediylgroup.

Examples of the divalent hydrocarbon group where a methylene group hasbeen replaced by an oxygen atom or carbonyl group include thoserepresented by formulae (L1-1) to (L1-4).

In these formulae, * represents a binding position to an oxygen atom.

X^(x1) is a carbonyloxy group or an oxycarbonyl group; and

L^(x1) is a C1-C16 divalent aliphatic saturated hydrocarbon group, andL^(x2) is a single bond or a C1-C15 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x1) and L^(x2) is 16 or less.

L^(x3) is a C1-C17 divalent aliphatic saturated hydrocarbon group, andL^(x4) is a single bond or a C1-C16 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x3) and L^(x4) is 17 or less.

L^(x5) is a C1-C15 divalent aliphatic saturated hydrocarbon group, andL^(x6) and L^(x7) are a single bond or a C1-C14 divalent chain oralicyclic hydrocarbon group, provided that the total number of thecarbon atoms in L^(x5), L^(x6) and L^(x7) is 15 or less.

L^(x8) and L^(x9) are each independently a single bond or a C1-C12divalent chain or alicyclic hydrocarbon group, and W^(x1) is a C3-C15divalent cyclic saturated hydrocarbon group, provided that the totalnumber of the carbon atoms in L^(x8), L^(x9) and W^(x1) is 15 or less.

L^(x1) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x2) is preferably a single bond, or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond.

L^(x3) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x4) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond, a methylenegroup or an ethylene group.

L^(x5) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x6) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x7) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x8) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

L^(x9) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

W^(x1) is a preferably C3-C10 divalent cyclic saturated hydrocarbongroup, more preferably a cyclohexanediyl group or an adamantanediylgroup.

Examples of the group represented by formula (L1-1) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-2) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-3) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-4) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

L⁵⁵ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit represented by formula (a5-1) includethe following ones and those where a methyl group has been replaced by ahydrogen atom in each formula.

When Resin (A) has the structural unit (a5), its content is preferably 1to 30% by mole, more preferably 2 to 20% by mole and still morepreferably 3 to 15% by mole based on 100% by mole of all the structuralunits of the resin.

<Structural Unit (II)>

Resin (A) may comprise a structural unit decomposed by irradiation togenerate an acid. Said structural unit is referred to as “the structuralunit (II)”. Examples of the structural unit (II) include one asdescribed in JP2016-79235A1.

The structural unit (II) preferably comprises a sulfonate or carboxylategroup and an organic cation, or a S* group and an organic anion at itsside chain.

The structural unit (II) which comprises a sulfonate or carboxylategroup and an organic cation at its side chain is preferably representedby formula (II-2-A′):

wherein X^(III3) represents a C1-C18 divalent saturated hydrocarbongroup in which a methylene group can be replaced by —O—, —S— or —CO— andin which a hydrogen atom can be replaced by a fluorine atom, a hydroxylgroup or a C1-C6 alkyl group which may have a fluorine atom,

A^(x1) represents a C1-C8 alkanediyl group in which a hydrogen atom canbe replaced by a fluorine atom or a C1-C6 perfluoroalkyl group, RA⁻represents a sulfonate or carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or a C1-C6 alkylgroup in which a hydrogen atom can be replaced by a halogen atom, andZA⁺ represents an organic cation.

For R^(III3), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(III3), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(x1), examples of the alkanediyl group include a methylene group,an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, an ethane-1,1-diylgroup, a propane-1,1-diyl group, a propane-1,2-diyl group, apropane-2,2-diyl group, a pentane-2,4-diyl group, a2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group,pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group.

For X^(III3), examples of divalent aliphatic hydrocarbon groups includea linear alkanediyl group, a branched alkanediyl group, a monocyclicalicyclic hydrocarbon, a polycyclic alicyclic hydrocarbon, and anycombinations of these groups, specific examples of which include alinear alkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diylgroup, a pentane-1,5-diyl group, a hexane-1,6-diyl group, aheptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diylgroup, a decane-1,10-diyl group, an undecane-1,11-diyl group, adodecane-1,12-diyl group;

a branched alkanediyl group such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and divalent polycyclic alicyclichydrocarbon groups such as norbornane-1,4-diyl group,norbornane-2,5-diyl group, adamantane-1,5-diyl group, andadamantane-2,6-diyl group.

Examples of the saturated hydrocarbon group in which a methylene grouphas been replaced by —O—, —S— or —CO— include divalent groupsrepresented by the formulae (X1) to (X53).

In each formula, X³ represents a C1-C16 divalent hydrocarbon group, X⁴represents a C1-C15 divalent hydrocarbon group, X⁵ represents a C1-C13divalent hydrocarbon group, X⁶ represents a C1-C14 divalent hydrocarbongroup, X7 represents a C1-C14 divalent hydrocarbon group, and X⁸represents a C1-C13 divalent hydrocarbon group and * represents abinding position to A^(x1), provided that each divalent grouprepresented by one of formulae (X1) to (X53) has 1 to 17 carbon atoms intotal.

Examples of the organic cation represented by ZA⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

Among them, an organic sulfonium cation and an organic iodonium cationare preferred, and a sulfonium cation, specifically an arylsulfoniumcation, is more preferred.

The structural unit represented by formula (II-2-A′) is preferablyrepresented by formula (II-2-A):

wherein X^(III3), R^(III3) and ZA⁺ are as defined above;

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a C1-C6 perfluoroalkyl group;

z represents an integer of 0 to 6; and

Q^(a) and Q^(b) each independently represent a fluorine atom or a C1-C6perfluoroalkyl group.

For Q⁸, Q^(b), R^(III2) and R^(III4), examples of a perfluoroalkyl groupinclude a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentylgroup and a tridecafluorohexyl group, and a trifluoromethyl group ispreferred.

The structural unit represented by formula (II-2-A) is preferablyrepresented by formula (II-2-A-1):

wherein R^(III2), R^(III3), R^(III4), Q^(a), Q^(b), z and ZA⁺ are asdefined above; R^(III5) represents a C1-C12 saturated hydrocarbon group,and X^(I2) represents a C1-C18 divalent saturated hydrocarbon group inwhich a methylene group can be replaced by —O—, —S— or —CO— and in whicha hydrogen atom can be replaced by a halogen atom or a hydroxyl group.

For R^(III5), examples of the saturated hydrocarbon group include chainalkyl groups such as methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, apentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group and adodecyl group.

For X^(I2), examples of the divalent saturated hydrocarbon group includethe same examples as the divalent saturated hydrocarbon group forX^(III3).

The structural unit represented by formula (II-2-A-1) is preferablyrepresented by formula (II-2-A-2):

wherein R^(III3), R^(III5), and ZA⁺ are as defined above; and n and meach independently represent 1 or 2.

Examples of the structural unit represented by formula (II-2-A′) includethe following ones and those recited in WO2012/050015A1.

The structural unit (II) which comprises a S⁺ group and an organic anionat its side chain is preferably represented by formula (II-1-1):

wherein A^(II1) represents a single bond or a divalent connecting group,R^(II1) represents a C6-C18 divalent aromatic hydrocarbon group, R^(II2)and R^(II3) each independently represent a C1-C18 hydrocarbon group orjointly represents a ring structure together S⁺ bonded thereto, R^(II4)represents a hydrogen atom, a halogen atom or a C1-C6 alkyl group inwhich a hydrogen atom can be replaced by a halogen atom, and A⁻represents an organic anion.

For R^(II1), examples of the aromatic hydrocarbon group include aphenylene group and naphthylene group.

For R^(II2) and R^(II3), examples of the hydrocarbon group include thealkyl groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groupsand any combination of these groups.

For R^(II4), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(II4), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(II1), examples of the divalent connecting group include a C1-C18divalent saturated hydrocarbon group in which a methylene group can bereplaced by —O—, —S— or —CO—. Specific examples of the divalentconnecting group include the same saturated hydrocarbon grouprepresented by X^(III3).

Examples of cation of the structural unit represented by formula(II-1-1) include the following ones.

Examples of the organic anion represented by A⁻ include a sulfonateanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxylateanion.

Among them, a sulfonate anion is preferred. For A⁻, a sulfonate anion ispreferably the same one as used for the salt represented by formula(B1).

For A⁻, examples of a sulfonylimide anion include the following ones.

For A⁻, examples of a sulfonylmethide anion include the following ones.

For A⁻, examples of a carbonyloxy anion include the following ones.

Examples of the structural unit represented by formula (II-1-1) includethe following ones.

When Resin (A) has the structural unit (II), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole, still more preferably3 to 10% by mole, based on 100% by mole of all the structural units ofthe resin.

Resin (A) is generally one which consists of the structural unit (I),one which consists of the structural unit (I) and a structural unit(a1), one which consists of the structural unit (I) and a structuralunit (s), or one which consists of the structural unit (I), a structuralunit (a1) and a structural unit (s). Examples of Resin (A) whichconsists of the structural unit (I), a structural unit (a1) and astructural unit (s) include one which has the structural unit (I), astructural unit (a1), a structural unit (a2) or (a3) and the structuralunit (a4), and one which has the structural unit (I), a structural unit(a1), a structural unit (a2) or (a3), a structural unit (a4) and astructural unit (a5). The structural unit (a1) is preferably oneselected from the group consisting of the structural unit (a1-0), thestructural unit (a1-0X), the structural unit (a1-1) and the structuralunit (a1-2), particularly that is one having a cyclohexyl group or acyclopentyl group. More preferably, Resin (A) has two structural unitsselected from the group consisting of the structural unit (a1-0), thestructural unit (a1-0X), the structural unit (a1-1) and the structuralunit (a1-2), particularly that is one having a cyclohexyl group or acyclopentyl group.

The structural unit (s) is preferably one selected from the groupconsisting of the structural unit (a2) and the structural unit (a3). Thestructural unit (a2) is preferably the structural unit (a2-1). Thestructural unit (a3) is preferably the structural unit (a3-1), thestructural unit (a3-2) and the structural unit (a3-4). Resin (A) can beproduced according to known polymerization methods such as radicalpolymerization.

The resin has usually 2,000 or more of the weight-average molecularweight, preferably 2,500 or more of the weight-average molecular weight,more preferably 3,000 or more of the weight-average molecular weight.The resin has usually 50,000 or less of the weight-average molecularweight, more preferably 30,000 or less of the weight-average molecularweight, and more preferably 15,000 or less of the weight-averagemolecular weight.

The weight-average molecular weight can be measured with gel permeationchromatography.

The composition of the present disclosure may have another resin thanResin (A).

Another resin than Resin (A) comprises no structural unit (I).

Examples of another resin than Resin (A) include one which comprises nostructural unit (I) but the structural unit (a1) [this resin issometimes referred to as “Resin (A2)” ], and one which consists of thestructural unit (a4) or which consists of the structural unit (a4) andthe structural unit (a5) [this resin is sometimes referred to as “Resin(X)” ].

In Resin (X), the content of the structural unit (a4) is preferably 30%by mole or more, more preferably 40% by mole or more, still morepreferably 45% by mole or more based on the sum of the structural unitsin the resin.

Resin (X) usually has 6000 or more of the weight-average molecularweight, preferably 7000 or more of the weight-average molecular weight.The resin usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography. When thephotoresist composition contains Resin (X), the content of the resin ispreferably 1 to 60 weight parts, more preferably 1 to 50 weight parts,and still more preferably 1 to 40 weight parts, further more preferably1 to 30 weight parts, further still more preferably 1 to 8 weight parts,relative to 100 parts of Resin (A).

The total content of the resins in the photoresist composition of thepresent invention is usually 80% by mass or more, preferably 90% by massor more, based on the sum of solid components, and usually 99% by massor less based on the sum of solid components. In this specification,“solid component” means components other than a solvent in thephotoresist composition.

The resin can be obtained by conducting polymerization reaction of thecorresponding monomer or monomers. The polymerization reaction isusually carried out in the presence of a radical initiator.

This polymerization reaction can be conducted according to knownmethods.

The composition of the present disclosure comprises a salt representedby formula (B1):

Q^(b1) and Q^(b2) independently each represent a fluorine atom or aC1-C6 perfluoroalkyl group,

L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group has been replaced by —CO—, in which a methylene groupcan be replaced by —O— and in which a hydrogen atom can be replaced by afluorine atom or a hydroxyl group,

Y represents a methyl group in which a hydrogen atom can be replaced bya substituent or a C3-C18 alicyclic hydrocarbon group in which ahydrogen atom can be replaced by a substituent and in which a methylenegroup can be replaced by —O—, —S(O)₂— or —CO—, and Z* represents anorganic cation.

Hereinafter, the salt will be simply referred to as “salt (B1)”. ForQ^(b1) and Q^(b2), examples of a perfluoroalkyl group include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group, and a trifluoromethyl group is preferred.

Q^(b1) and Q^(b2) each independently preferably represent a fluorineatom or a trifluoromethyl group, and Q^(b1) and Q^(b2) are morepreferably fluorine atoms.

For L^(b1), examples of the divalent saturated hydrocarbon group includelinear alkylene groups such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, atridecane-1,13-diyl group, a tetradecane-1,14-diyl group, apentadecane-1,15-diyl group, a hexadecane-1,16-diyl group andheptadecane-1,17-diyl group; branched alkylene groups such as anethane-1,1-diyl group, a propane-1,1-diyl group, a propane-1,2-diylgroup, a propane-2,2-diyl group, a pentane-2,4-diyl group, a2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group,pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group;

divalent monocyclic alicyclic hydrocarbon groups such ascyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group,cyclohexane-1,4-diyl group and cyclooctane-1,5-diyl group; and divalentpolycyclic alicyclic hydrocarbon groups such as norbornane-1,4-diylgroup, norbornane-2,5-diyl group, adamantane-1,5-diyl group andadamantane-2,6-diyl group.

For L^(b1), examples of the saturated hydrocarbon group in which amethylene group has been replaced by an oxygen atom or a carbonyl groupinclude those represented by formulae (b1-1) and (b1-2).

In formula (b1-1), L^(b2) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b3) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that the totalnumber of the carbon atoms of L^(b2) and L^(b3) is up to 22.

In formula (b1-2), L^(b4) represents a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, and L^(b)5 represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that the total carbon atomsof L^(b4) and L^(b5) is up to 22.

In these formulae, * represents a binding position to Y.

In formulae (b1-1) and (b1-2), the divalent saturated hydrocarbon groupincludes linear chain alkanediyl groups, branched chain alkanediylgroups, monocyclic or polycyclic divalent saturated hydrocarbon groups,and a group combining two or more of the above-mentioned groups.

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b4) is preferably a C1-C8 divalent saturated hydrocarbon group wherea hydrogen atom may be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

Examples of the group represented by formula (b1-1) include thoserepresented by formulae (b1-4), (b1-5), (b1-6), (b1-7), (b1-8), (b1-9),(b1-10) and (b1-11).

In formula (b1-4), L^(b8) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom or a hydroxyl group.

In formula (b1-5), L^(b9) represents a C1-C20 divalent saturatedhydrocarbon group, and L^(b10) represents a single bond or a C1-C19divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, provided that the totalcarbon atoms of L^(b10) and L^(b9) is up to 20.

In formula (b1-6), L^(b11) represents a C1-C21 divalent saturatedhydrocarbon group, and L^(b12) represents a single bond or a C1-C20divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b11) and L^(b12) is up to 21.

In formula (b1-7), L^(b13) represents a C1-C19 divalent saturatedhydrocarbon group, L^(b14) represents a single bond or a C1-C18 divalentsaturated hydrocarbon group, and L^(b15) represents a single bond or aC1-C18 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b13), L^(b14) and L^(b15) is up to 19.

In formula (b1-8), L^(b16) represents a C1-C18 divalent saturatedhydrocarbon group, L^(b17) represents a C1-C18 divalent saturatedhydrocarbon group, and L^(b18) represents a single bond or a C1-C17divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b16), L^(b17) and L^(b18) is up to 19.

In formula (b1-10), L^(b21) represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom, L^(b22) represents a single bond or aC1-C21 divalent saturated hydrocarbon group and L^(b23) represents asingle bond or a C1-C21 divalent saturated hydrocarbon group where ahydrogen atom may be replaced by a hydroxyl group or a fluorine atom andwhere a methylene group may be replaced by an oxygen atom or a carbonylgroup, provided that the total carbon atoms of L^(b21), L^(b22) andL^(b23) is up to 21.

In formula (b1-11), L^(b24) represents a C1-C21 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b25) represents a C1-C21 divalent saturated hydrocarbon group,and L^(b26) represents a single bond or a C1-C20 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or a carbonyl group, provided that the total carbon atomsof L^(b24), L^(b25) and L^(b26) is up to 21.

In these formulae,* represents a binding position to Y.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups. Specificexamples of the divalent saturated hydrocarbon group include those asreferred to for L^(b1).

L^(b8) is preferably a C1-C4 alkanediyl group.

L^(b9) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1-C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b11) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b16) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b17) is preferably a C1-C6 divalent saturated hydrocarbon group.

L^(b18) is preferably a single bond or a C1-C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C4 divalentsaturated hydrocarbon group.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups.

Specific examples of the divalent saturated hydrocarbon group includethose as referred to for L^(b1).

Examples of the divalent saturated hydrocarbon group where a methylenegroup has been replaced by an oxygen atom or a carbonyl group includethe divalent saturated hydrocarbon group that has an acyloxy group.

In the divalent saturated hydrocarbon group that has an acyloxy group, ahydrogen atom may be replaced by a hydroxyl group and a methylene groupmay be replaced by an oxygen atom or a carbonyl group.

Examples of the divalent saturated hydrocarbon group which has anacyloxy group include an acetyloxy group, a propionyloxy group, abutyryloxy group, a cyclohexylcarbonyloxy group and anadamantylcarbonyloxy group.

When a hydrogen atom has been replaced by a hydroxyl group or amethylene group has been replaced by an oxygen atom or a carbonyl groupin the divalent saturated hydrocarbon group that has an acyloxy group,examples of such a group include an oxoadamantylcarbonyloxy group, ahydroxyadamantylcarbonyloxy group, an oxocyclohexylcarbonyloxy group,and a hydroxycyclohexylcarbonyloxy group.

Examples of the group represented by formula (b1-4) include thefollowing ones.

Examples of the group represented by formula (b1-5) include thefollowing ones.

Examples of the group represented by formula (b1-6) include thefollowing ones.

Examples of the group represented by formula (b1-7) include thefollowing ones.

Examples of the group represented by formula (b1-8) include thefollowing ones.

Examples of the group represented by formula (b1-9) include thefollowing ones.

Examples of the group represented by formula (b1-10) include thefollowing ones.

Examples of the group represented by formula (b1-11) include thefollowing ones.

Examples of the group represented by formula (b1-2) include thefollowing ones.

The monovalent alicyclic hydrocarbon group for Y may be a monocyclic oneor polycyclic one such as a spiro ring.

Preferred examples of the alicyclic hydrocarbon group represented by Yinclude those represented by the formulae (Y1) to (Y11) and (Y36) to(Y38). Preferred examples of the alicyclic hydrocarbon group which isrepresented by Y and in which a methylene group has been replaced by—O—, —SO₂— or —CO— include those represented by the formulae (Y12) to(Y35) and Y(39) and Y(41).

Among the groups represented by the formulae, preferred are thoserepresented by formulae (Y1) to (Y20), (Y30), (Y31), and (Y39) to (Y41);more preferred are those represented by the formulae (Y11), (Y15),(Y16), (Y20), (Y30), (Y31) and (Y39) to (Y41); and still more preferredare those represented by the formulae (Y11), (Y15), (Y30), (Y39) and(Y40).

Substituents on the methyl group for Y include a halogen atom, ahydroxyl group, a C3-C16 alicyclic hydrocarbon group, a C6-C18 aromatichydrocarbon group, a glycidyloxy group, and —(CH₂)_(j2)—O—CO—R^(b1′)— inwhich R^(b1′) is a C1-C16 alkyl group, a C3-C16 alicyclic hydrocarbongroup, or a C6-C18 aromatic hydrocarbon group and j2 is an integer of 0to 4.

Substituents on the alicyclic hydrocarbon groups for Y include a halogenatom, a hydroxyl group, a C1-C12 alkyl group, a C1-C12hydroxy-containing alkyl group, a C1-C12 alkoxy group, a C3-C16alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon group, aC7-C21 aralkyl group, a C2-C4 acyl group, a glycidyloxy group, and—(CH₂)_(j2)—O—CO—R^(b1′)— in which R^(b1′) is a C1-C16 alkyl group andj2 is an integer of 0 to 4.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group, anorbornyl group and an adamantyl group.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group and a dodecyl group.

Examples of hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of the C1-C12 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxygroup, a heptyloxy group, an octyloxy group, a decyloxy group and adodecyloxy group.

Examples of the aralkyl group include a benzyl group, phenylpropylgroup, a phenethyl group, a naphthylmethyl group, or a naphthylethylgroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of Y include the groups as follow.

Y represents preferably a C3-C18 alicyclic hydrocarbon group which mayhave a substituent and in which a methylene group may be replaced by—O—, —SO₂— or —CO—, more preferably an adamantyl group which may have asubstituent and in which a methylene group may be replaced by —O—, —SO₂—or —CO—, and still more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or the following groups.

where * represents a binding position.

Preferred examples of the sulfonic acid anion of the salt represented byformula (B1) include salts represented by the formulae (B1-A-1) to(B1-A-55), preferablythe formulae (B1-A-1) to (B1-A-4), (B1-A-9),(B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40) and (B1-A-47)to (B1-A-55).

In these formulae, the symbols Q^(b1) and Q^(b2) are defined as above,R^(i2), R^(i3), R^(i4), R^(i5), R^(i6) and R^(i7) each independentlyrepresent a C1-C4 alkyl group, preferably a methyl group or an ethylgroup, R^(i8) represents a C1-C12 aliphatic hydrocarbon group[preferably a C1-C4 alkyl group], a C5-C12 monovalent alicyclichydrocarbon group, or a combined group of them, preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group, andL^(A4) represents a single bond or a C1-C4 alkanediyl group.

Examples of the sulfonic acid anion of the salt represented by formula(B1) include those described in JP2010-2046465A1. Specific examples ofthe sulfonic acid anion of the salt represented by formula (B1) includethe following anions.

Among them, preferred are those represented by formulae (B1a-1) to(B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22) to(B1a-30).

Examples of the organic cation represented by Z⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

Among them, an organic sulfonium cation and an organic iodonium cationare preferred, and a sulfonium cation, specifically an arylsulfoniumcation, is more preferred.

Preferred examples of the cation include those represented by theformulae (b2-1), (b2-2), (b2-3) and (b2-4):

In the formulae (b2-1) to (b2-4), R^(b4), R^(b5) and R^(b6)independently represent a C1-C30 aliphatic hydrocarbon group, a C3-C36alicyclic hydrocarbon group and a C6-C36 aromatic hydrocarbon group. Thealiphatic hydrocarbon group can have a substituent selected from thegroup consisting of a hydroxy group, a C1-C12 alkoxy group, a C3-C12alicyclic hydrocarbon group and a C6-C18 aromatic hydrocarbon group. Thealicyclic hydrocarbon group can have a substituent selected from thegroup consisting of a halogen atom, a C1-C18 aliphatic hydrocarbongroup, a C2-C4 acyl group and a glycidyloxy group. The aromatichydrocarbon group can have a substituent selected from the groupconsisting of a halogen atom, a hydroxy group, a C1-C18 aliphatichydrocarbon group and a C1-C12 alkoxy group.

-   -   R^(b4) and R^(b5) can be bonded to form a ring together with the        adjacent S*, and a methylene group in the ring may be replaced        by —CO—, —O— or —SO—.

R^(b7) and R^(b8) are independently in each occurrence a hydroxy group,a C1-C12 aliphatic hydrocarbon group or a C1-C12 alkoxy group, m2 and n2each independently represents an integer of 0 to 5.

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group.

R^(b9) and R^(b10) can be bonded to form a ring together with theadjacent S*, and a methylene group in the divalent alicyclic hydrocarbongroup may be replaced by —CO—, —O— or —SO—.

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group.

R^(b12) represents a C1-C12 aliphatic hydrocarbon group in which ahydrogen atom can be replaced by a C6-C18 aromatic hydrocarbon group, aC3-C18 saturated cyclic hydrocarbon group and a C6-C18 aromatichydrocarbon group in which a hydrogen atom can be replaced by a C1-C12alkoxy group or a (C1-C12 alkyl)carbonyloxy group.

R^(b11) and R^(b12) can be bonded each other to form a C1-C10 divalentalicyclic hydrocarbon group which forms a 2-oxocycloalkyl group togetherwith the adjacent —CHCO—, and a methylene group in the divalentalicyclic hydrocarbon group may be replaced by —CO—, —O— or —SO—.

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) independentlyrepresent a hydroxy group, a C1-C12 aliphatic hydrocarbon group or aC1-C12 alkoxy group.

L^(b31) represents —S— or —O— and o2, p2, s2 and t2 each independentlyrepresents an integer of 0 to 5, q2 and r2 each independently representsan integer of 0 to 4, and u2 represents 0 or 1.

Preferred examples of the aliphatic hydrocarbon group represented byR^(b4) to R^(b12) include an alkyl group such as a methyl group, anethyl group, a n-propyl group, an isopropyl group, a n-butyl group,sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, anoctyl group and 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9), R^(b10), R^(b11) and R^(b12) has preferably 1 to12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic one.Preferred examples of the monocyclic hydrocarbon group include acycloalkyl group such as a cyclopentyl group, a cyclohexyl group, amethylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl groupand a cyclooctyl group. Preferred examples of the polycyclic hydrocarbongroup include an adamantyl group, a norbornyl group and adecahydronaphtyl group, and the following groups.

The alicyclic hydrocarbon group represented by R^(b9), R^(b10), R^(b11)and R^(b12) has preferably 3 to 18 carbon atoms, more preferably 4 to 12carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornylgroup, and an isonorbornyl group.

The alicyclic hydrocarbon group in which a hydrogen atom has beenreplaced by an aliphatic hydrocarbon group has preferably 20 or lesscarbon atoms in total.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, tolyl group, xylyl group, cumenyl group, mesityl group,p-ethylphenyl group, p-tert-butylphenyl group, p-adamantylphenyl group,a biphenylyl group, a naphthyl group, a phenanthryl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group.

When the aromatic hydrocarbon group has an alicyclic hydrocarbon groupor an aliphatic hydrocarbon group, it is preferred that the alicyclichydrocarbon group and the aliphatic hydrocarbon group have respectively1 to 18 carbon atoms and 3 to 18 carbon atoms.

Examples of the aromatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an alkoxy group include p-methoxyphenyl group.

Examples of the aliphatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aromatic hydrocarbon group include a benzyl group, aphenethyl group, a phenylpropyl group, trityl group, naphthylmethylgroup, and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group,apropoxygroup, abutoxygroup, a pentyloxygroup, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of alkylcarbonyloxy group include a methylcarbonyloxy group, anethylcarbonyloxy group, a n-propylcarbonyloxy group, anisopropylcarbonyloxy group, a n-butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethyl hexylcarbonyloxy group.

The ring group formed by bonding R^(b4) and R^(b5) together with theadjacent S*maybemonocyclicorpolycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring is generally 3 to12-memberedone, preferably 3 to 7-membered one. Examples of the ring include thefollowing ones.

The ring group formed by bonding R^(b9) and R^(b10) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include a thiolan-1-ium ring(tetrahydrothiphenium ring), a thian-1-ium ring and a 1,4-oxathian-4-iumring.

The ring group formed by bonding R^(b11) and R^(b12) together with—CH—CO— may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include an oxocycloheptanering, an oxocyclohexane ring, an oxonorbornane ring, and anoxoadamantane ring.

Preferred examples of the cation for the acid generator include anarylsulfonium cation, specifically cation of formula (b2-1), and morespecifically a phenylsulfonium cation.

Preferably, the cation of formula (b2-1) has one or three phenyl groups.When the cation of formula (b2-1) has one phenyl group, it has further athiolan-1-ium ring or a 1,4-oxathian-4-ium ring. Examples of the cationrepresented by the formula (b2-1) include the followings.

Examples of the cation represented by the formula (b2-2) include thefollowings.

Examples of the cation represented by the formula (b2-3) include thefollowings.

Examples of the cation represented by the formula (b2-4) include thefollowings.

Examples of the organic counter ion represented by Z⁺ include an oniumcation such as a sulfonium cation, an iodonium cation, an ammoniumcation, a benzothiazolium cation and a phosphonium cation, and asulfonium cation and an iodonium cation are preferred, and a sulfoniumcation, specifically an arylsulfonium cation, is more preferred.

The salt represented by formula (B1) may consist of the above-mentionedorganic counter ion and the above-mentioned sulfonic acid anion. Thesalt represented by formula (B1) preferably consists of an anionrepresented by any one of formulae (B1a-1) to (B1a-3), (B1a-7) to(B1a-16), (B1a-18), (B1a-19) and (B1a-22) to (B1a-34) and a cationrepresented by (b2-1) or (b2-3). Specific examples of the saltrepresented by formula (B1) include the following salts represented byformulae (B1-1) to (B1-48). Among them, those which comprise anarylsulfonium cation are preferred, the salts represented by formulae(B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to (B1-14), (B1-20) to(B1-26), (B1-29), (B1-31) to (B1-48) are more preferred.

The composition of the present disclosure may contain two or more kindsof the salt (B1).

The total content of the Salt (B1) is preferably 1 to 40 parts by mass,more preferably 3 to 35 parts by mass, per 100 parts of Resin (A).

The composition of the present disclosure may further comprise anothersalt than Salt (B1) as an acid generator.

In the photoresist composition, an acid generates from the acidgenerator by light for lithography. The acid catalytically acts againstan acid-labile group in the resin to cleave the acid-labile group.

The acid generator known in the art may be a nonionic acid generator oran ionic acid generator. Examples of the nonionic acid generator includean organo-halogen compound, a sulfonate compound such as a2-nitrobenzylsulfonate, an aromaticsulfonate, an oximesulfonate, anN-sulfonyloxyimide, a sulfonyloxyketone and diazonaphthoquinone4-sulfonate, and a sulfone compound such as a disulfone, a ketosulfoneand a sulfonyldiazomethane. Examples of the ionic acid generator includean onium salt compound such as a diazonium salt, a phosphonium salt, asulfonium salt and an iodonium salt. Examples of the anion of the oniumsalt include a sulfonic acid anion, a sulfonylimide anion and asulfonylmethide anion.

<Solvent>

Preferably, the photoresist composition of the disclosure furthercontains a solvent.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more, more preferably 94% by weight or more based ontotal amount of the photoresist composition of the present invention.The amount of the solvent is usually 99.9% by weight or less andpreferably 99% by weight or less based on total amount of thephotoresist composition of the present invention. The content can bemeasured with known methods such as liquid chromatography or gaschromatography.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; a glycol ether such as propylene glycolmonomethyl ether; an ester such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; a ketone such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and a cyclic ester such asγ-butyrolactone.

<Quencher>

The photoresist composition of the disclosure may further contain aquencher such as a basic compound. The “quencher” has the property thatit can trap an acid, especially an acid generated from the acidgenerator by exposure to light for lithography.

Examples of the quencher include a basic compound, such as a basicnitrogen-containing organic compound, and a salt which generates an acidhaving acidity weaker than an acid generated from the acid generators.

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine and anammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-,3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, dioctylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris [2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenyl methane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy) ethane, di(2-pyridyl) ketone,4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

As to salt which generates an acid having acidity weaker than an acidgenerated from the acid generators, the acidity in the salts is shown bythe acid dissociation constant (pKa).

The acid dissociation constant of acid generated from the salt for aquencher is usually −3<pKa.

The salt for a quencher is preferably a salt of −1<pKa<7, and morepreferably a salt of 0<pKa<5.

Specific examples of the salt for a quencher include the following ones,an onium carboxylic acid salt such as the salt of formula (D), and saltsrecited in US2012/328986A1, US2011/171576A1,

US2011/201823A1, JP2011-39502A1, and US2011/200935A1. The photoresistcomposition comprises preferably onium carboxylic acid salt, morepreferably the salt of formula (D).

In formula (D), R^(D1) and R^(D2) respectively represent a C1-C12monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom. The symbols m′ and n′ each independently represent aninteger of 0 to 4, preferably an integer of 0 to 2, more preferably 0.

Examples of the compounds of formula (D) include the following ones.

The content of quencher is preferably 0.01 to 5% by mass, and morepreferably 0.01 to 3% by mass, based on the sum of solid components. Thephotoresist compositions of the present invention may comprise, ifnecessary, a small amount of various additives suchasa sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the present invention can be prepared bymixing, usually in a solvent, an acid generator which contains the salt(B1) and Resin (A), and if necessary Resin (A2), Resin (X), a quencher,and/or additives at a suitable ratio for the composition, optionallyfollowed by filtrating the mixture with a filter having 0.003 μm to 0.2μm of a pore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like. The mixing timeis usually 0.5 to 24 hours, which can be selected in view of thetemperature. The means for mixing the components is not limited tospecific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

-   -   (1) a step of applying the photoresist composition of the        present invention on a substrate,    -   (2) a step of forming a composition film by conducting drying,    -   (3) a step of exposing the composition film to radiation,    -   (4) a step of baking the exposed composition film, and    -   (5) a step of developing the baked composition film.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Examplesof the substrate include a silicon wafer or a quartz wafer on which asensor, a circuit, a transistor or the like is formed.

The formation of the composition film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature is usually 50 to 200° C. When the pressure is reduced duringheating, the operation pressure is usually 1 to 1.0*10⁵ Pa. The heatingtime is usually 10 to 180 seconds.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) anda F₂ laser (wavelength: 157 nm), alight source radiating harmonic laser light in a far UV region or avacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser), and a lightsource radiating electron beam or EUV (extreme ultraviolet) light.

The temperature of baking of the exposed composition film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked composition film is usually carried outusing a development apparatus. The development method includes dippingmethods, paddle methods, spray methods and dynamic dispense method. Thedeveloping temperature is preferably 5 to 60° C., and the developingtime is preferably 5 to 300 seconds.

The positive and negative type photoresist patterns can be obtained bythe development depending on a developer to be used therefor. When apositive type photoresist pattern is prepared from the photoresistcomposition of the present invention, the development can be conductedwith an alkaline developer. The alkaline developer to be used may be anyone of various alkaline aqueous solution used in the art. Generally, anaqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”.

Examples of an organic solvent for organic developer include ketonesolvents such as 2-hexanone, 2-heptanone; glycolether ester solventssuch as propyleneglycolmonomethylether acetate; ester solvents such asbutyl acetate; glycolether solvents such aspropyleneglycolmonomethylether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of organic solvent is preferably from 90% to 100% by weight,more preferably from 95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from90% to 100% by weight, more preferably from 95% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by a rinse agent. The rinse agent is not limited to anyspecific one, as long as it does not dissolve a photoresist composition.Examples of the rinse agent include an organic solvent which contains,for example, an alcohol solvent or an ester solvent.

The photoresist composition of the present invention is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EUV (extremeultraviolet) lithography, EUV immersion lithography and EB (electronbeam) lithography.

EXAMPLES

The present invention will be described more specifically by Examples,which are not construed to limit the scope of the present invention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatographyunder the following conditions.

Column: HLC-8120GPC Type (Three Columns with guard column), TSKgel

Multipore HXL-M, manufactured by TOSOH CORPORATION

Solvent: Tetrahydrofuran, Flow rate: 1.0 mL/min.

Detector: RI detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: Standard polystyrene

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.).

In the following examples, the value of the molecular ion peak isreferred to as “MASS”.

Synthesis Example 1

In a reactor, 25 parts of the compound represented by the formula(I-2-a), 4.61 parts of the compound represented by the formula (I-2-c),and 100 parts of chloroform were mixed and stirred at 23° C. for 30minutes. To the obtained mixture, 19.86 parts of the compoundrepresented by the formula (I-2-b) was added and then stirred at 23° C.for 2 hours.

To the reaction mixture, 180 parts of chloroform and 155 parts of 10%aqueous potassium carbonate solution were added and then stirred at 23°C. for 30 minutes. Then the obtained organic layer was collectedtherefrom.

To the collected organic layer, 60 parts of ion-exchanged water wasadded and then stirred at 23° C. for 30 minutes for washing, followed byseparating into an organic layer. The organic layer was washed withwater four times as mentioned above.

Then the resultant mixture was concentrated, and the concentrates wereseparated by silica gel column chromatography [silica gel 60N (sphericalshape, neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=5/1] to obtain 38.89 parts of the compound represented byformula (I-2-d).

In a reactor, 38.86 parts of the compound represented by the formula(I-2-d) and 200 parts of acetonitrile were mixed and then stirred at 23°C. for 30 minutes, and then cooled to 5° C.

To the obtained mixture, a mixture composed of 3.53 parts of sodiumborohydride and 52.95 parts of ion-exchanged water was added and thenstirred at 23° C. for 18 hours.

Then the reaction mixture was concentrated, and thereto 230 parts oftert-butylmethylether and 90 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating into anorganic layer. Then the obtained organic layer was collected therefrom.The organic layer was washed five times as mentioned above. Then theresultant mixture was concentrated, and the concentrates were separatedby silica gel column chromatography [silica gel 60N (spherical shape,neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=5/1] to obtain 36.93 parts of the salt represented by formula(I-2-e).

In a reactor, 36.93 parts of the compound represented by the formula(I-2-e), 30.56 parts of pyridine, 8.58 parts of dimethylaminopyridine,and 180 parts of methylisobutylketone were mixed, and stirred at 23° C.for 30 minutes, followed by cooling to 5° C.

To the obtained mixture, 32.9 parts of the compound represented byformula (I-2-f) were added, and stirred at 23° C. for 18 hours.

Then 300 parts of n-heptane and 150 parts of 10% aqueous potassiumcarbonate solution were stirred at 23° C. for 30 minutes, followed byseparating into an organic layer. To the collected organic layer, 90parts of ion-exchanged water was added and then stirred at 23° C. for 30minutes for washing, followed by separating into an organic layer. Theorganic layer was washed with water five times as mentioned above.

To the collected organic layer, 160 parts of 5% aqueous oxalic acidsolution was added and then stirred at 23° C. for 30 minutes forwashing, followed by separating into an organic layer.

To the collected organic layer, 90 parts of ion-exchanged water wasadded and then stirred at 23° C. for 30 minutes for washing, followed byseparating into an organic layer. The organic layer was washed withwater five times as mentioned above.

Then the resultant mixture was concentrated, and the concentrates wereseparated by silica gel column chromatography [silica gel 60N (sphericalshape, neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=5/1] to obtain 33.66 parts of the salt represented by formula(I-2).

MASS (MASS spectrum): 279.2 [M⁺+H]

Synthesis Example 2

In a reactor, 0.93 parts of the compound represented by the formula(I-2) and 3 parts of methylisobutylketone were mixed and stirred at 23°C. for 30 minutes. To the obtained mixture, 2.4 parts of the 2.5%aqueous p-toluene sulfonic acid solution was dropped and then stirred at23° C. for 18 hours.

To the reaction mixture, 10 parts of methylisobutylketone and 5 parts ofion-exchanged water were added and then stirred at 23° C. for 30minutes. Then the obtained organic layer was collected therefrom.

To the collected organic layer, 5 parts of ion-exchanged water was addedand then stirred at 23° C. for 30 minutes for washing, followed byseparating into an organic layer. The organic layer was washed withwater five times as mentioned above.

To the collected organic layer, 5 parts of ion-exchanged water was addedand then stirred at 23° C. for 30 minutes for washing, followed byseparating into an organic layer. The organic layer was washed withwater five times as mentioned above.

Then the resultant mixture was concentrated, and the concentrates wereseparated by silica gel column chromatography [silica gel 60N (sphericalshape, neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=1/1] to obtain 0.33 parts of the compound represented by formula(I-1).

MASS (MASS spectrum): 207.1 [M+H]⁺

Synthesis Example 3

In a reactor, 1.87 parts of the compound represented by the formula(I-1), 1.22 parts of dimethylaminopyridine, and 30 parts oftetrahydrofuran were mixed and stirred at 23° C. for 30 minutes. To theobtained mixture, 1.98 parts of the compound represented by the formula(I-6-a) was added and then stirred at 40° C. for 18 hours.

To the reaction mixture, 50 parts of chloroform and 25 parts ofion-exchanged water were added and then stirred at 23° C. for 30minutes.

Then the obtained organic layer was collected therefrom.

To the collected organic layer, 10 parts of 10% aqueous potassiumcarbonate solution was added and then stirred at 23° C. for 30 minutesfor washing, followed by separating into an organic layer.

To the collected organic layer, 25 parts of ion-exchanged water wasadded and then stirred at 23° C. for 30 minutes for washing, followed byseparating into an organic layer. The organic layer was washed withwater four times as mentioned above.

Then the resultant mixture was concentrated, and the concentrates wereseparated by silica gel column chromatography [silica gel 60N (sphericalshape, neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=5/1] to obtain 1.22 parts of the compound represented by formula(I-6).

MASS (MASS spectrum): 307.2 [M⁺+H]

Synthesis Example 4

In a reactor, 1.87 parts of the compound represented by the formula(I-1), 1.22 parts of dimethylaminopyridine and 30 parts oftetrahydrofuran were mixed and stirred at 23° C. for 30 minutes.

To the obtained mixture, 2.23 parts of the compound represented by theformula (I-7-a) was added and then stirred at 40° C. for 18 hours.

To the reaction mixture, 50 parts of chloroform and 25 parts ofion-exchanged water were added and then stirred at 23° C. for 30minutes.

Then the obtained organic layer was collected therefrom. The organiclayer was washed with water four times as mentioned above.

Then the resultant mixture was concentrated, and the concentrates wereseparated by silica gel column chromatography [silica gel 60N (sphericalshape, neutral), 100 to 210 μm, Kanto Chemical, eluent: n-heptane/ethylacetate=5/1] to obtain 1.09 parts of the compound represented by formula(I-7).

MASS (MASS spectrum): 321.2 [M⁺+H]

Synthesis of Resin

Monomers used in the following Example are following monomers.

Those monomers are sometimes referred to as “Monomer (X)” in which (X)represents the sign of the formula corresponding to the monomer.

For example, the monomer represented by formula (a1-1-3) is referred toas “Monomer (a1-1-3)”.

Synthesis Example 5

Acetoxystyrene and monomer (I-2) were mixed in a molar ratio of 80/20(acetoxystyrene/monomer (I-2)), and methylisobutylketone was added in anamount of 1.5 times total parts of all monomers to prepare a mixture. Tothe mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then to the reaction mixture, 25wt % aqueous tetramethylammonium hydroxide solution in an amount of 2.0times total parts of all monomers was added and stirred for 12 hours,followed by performing separation. The reaction mixture obtained waspoured into a large amount of n-heptane to cause precipitation, followedby being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,500 was obtained in the yield of 52%.

That polymer is referred to as Resin A1.

Synthesis Example 6

Acetoxystyrene, monomer (I-2), monomer (a1-1-3) and monomer (a1-2-6)were mixed in a molar ratio of 34/22/22/22 (acetoxystyrene/monomer(I-2)/monomer (a1-1-3)/monomer (a1-2-6)), and methylisobutylketone wasadded in an amount of 1.5 times total parts of all monomers to prepare amixture. To the mixture, azobisisobutyronitrile as an initiator in aratio of 1.2 mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then to the reaction mixture, 25wt % aqueous tetramethylammonium hydroxide solution in an amount of 2.0times total parts of all monomers was added and stirred for 12 hours,followed by performing separation. The mixture was stirred for 6 hours,followed by performing separation. The reaction mixture obtained waspoured into a large amount of n-heptane to cause precipitation, followedby being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,400 was obtained in the yield of 58%. That polymer is referred to asResin A2.

Synthesis Example 7

The monomers (a1-4-2) and (I-2) were mixed in a molar ratio of 34/66(monomer (a1-4-2)/monomer (I-2)), and methylisobutylketone was added inan amount of 1.5 times total parts of all monomers to prepare a mixture.To the mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then the reaction mixture wascooled to 15° C., followed by adding 2.5 wt % aqueous p-toluenesulfonicacid solution in an amount of 2.0 times total parts of all monomersthereto. The mixture was stirred for 6 hours, followed by performingseparation. The reaction mixture obtained was poured into a large amountof n-heptane to cause precipitation, followed by being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,200 was obtained in the yield of 55%. That polymer is referred to asResin A3.

Synthesis Example 8

The monomers (a1-4-2), (I-2), (a1-1-3) and (a1-2-6) were mixed in amolar ratio of 34/22/22/22 (monomer (a1-4-2)/monomer (I-2)/monomer(a1-1-3)/monomer (a1-2-6)), and methylisobutylketone was added in anamount of 1.5 times total parts of all monomers to prepare a mixture. Tothe mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then the reaction mixture wascooled to 15° C., 2.5 wt % aqueous p-toluenesulfonic acid solution in anamount of 2.0 times total parts of all monomers was added thereto, andthe mixture was stirred for 6 hours, followed by performing separation.The reaction mixture obtained was poured into a large amount ofn-heptane to cause precipitation, followed by being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,500 was obtained in the yield of 58%. That polymer is referred to asResin A4.

Synthesis Example 9

The monomers (a2-2-1), (I-1), (a1-1-3) and (a1-2-6) were mixed in amolar ratio of 34/22/22/22 (monomer (a2-2-1)/monomer (I-1)/monomer(a1-1-3)/monomer (a1-2-6)), and methylisobutylketone was added in anamount of 1.5 times total parts of all monomers to prepare a mixture.

To the mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours.

The reaction mixture as obtained was poured into a large amount ofn-heptane to cause precipitation, followed by being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,300 was obtained in the yield of 60%. That polymer is referred to asResin A5.

Synthesis Example 10

The monomers (a1-4-2), (I-2), (a1-1-3), (a1-2-6) and (a3-4-2) were mixedin a molar ratio of 25/20/20/20/15 (monomer (a1-4-2)/monomer(I-2)/monomer (a1-1-3)/monomer (a1-2-6)/monomer (a3-4-2)), andmethylisobutylketone was added in an amount of 1.5 times total parts ofall monomers to prepare a mixture.

To the mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours.

Then the reaction mixture was cooled to 15° C., 2.5 wt % aqueousp-toluenesulfonic acid solution in an amount of 2.0 times total parts ofall monomers was added thereto, and the mixture was stirred for 6 hours,followed by performing separation. The reaction mixture obtained waspoured into a large amount of n-heptane to cause precipitation, followedby being filtrated. As a result, a polymer having a weight-averagemolecular weight of about 6, 400 was obtained in the yield of 62%. Thatpolymer is referred to as Resin A6.

Synthesis Example 11

Acetoxystyrene and the monomers (I-6), (a1-1-3) and (a1-2-6) were mixedin a molar ratio of 34/22/22/22 (acetoxystyrene/monomer (I-6)/monomer(a1-1-3)/monomer (a1-2-6)), and methylisobutylketone was added in anamount of 1.5 times total parts of all monomers to prepare a mixture. Tothe mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then the reaction mixture wascooled to 15° C., followed by adding 25 wt % aqueous tetramethylammoniumhydroxide solution in 2.0 times total parts of all monomers thereto. Themixture was stirred for 12 hours, followed by performing separation. Thereaction mixture obtained was poured into a large amount of n-heptane tocause precipitation, followed by being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,700 was obtained in the yield of 54%. That polymer is 5 referred to asResin A7.

Synthesis Example 12

Acetoxystyrene and the monomers (I-7), (a1-1-3) and (a1-2-6) were mixedin a molar ratio of 34/22/22/22 (acetoxystyrene/monomer (I-7)/monomer(a1-1-3)/monomer (a1-2-6)), and methylisobutylketone was added in anamount of 1.5 times total parts of all monomers to prepare a mixture. Tothe mixture, azobisisobutyronitrile as an initiator in a ratio of 1.2mol % based on all monomer molar amount andazobis(2,4-dimethylvaleronitrile) as an initiator in a ratio of 3.6 mol% based on all monomer molar amount were added, and the obtained mixturewas heated at 73° C. for about 5 hours. Then 25 wt % aqueoustetrametylammonium hydroxide solution in 2.0 times total parts of allmonomers was added thereto, and the mixture was stirred for 12 hours,followed by performing separation. The reaction mixture obtained waspoured into a large amount of n-heptane to cause precipitation, followedby being filtrated.

As a result, a polymer having a weight-average molecular weight of about6,900 was obtained in the yield of 51%. That polymer is referred to asResin A8.

Examples 1 to 16 and Comparative Examples 1 and 2

<Producing Photoresist Compositions>

The following components as listed in the following table were mixed anddissolved in the solvent as mentioned below, and then filtrated througha fluorine resin filter having pore diameter of 0.2 μm, to preparephotoresist compositions.

TABLE 1 Resin Acid generator Quencher Comp. (kind/amount (kind/amount(kind/amount PB(° C.)/PEB No. (part)) (part)) (part)) (° C.) 1 A1/10B1-43/3.4 C1/0.7 110/120 2 A2/10 B1-43/3.4 C1/0.7 110/120 3 A3/10B1-43/3.4 C1/0.7 110/120 4 A4/10 B1-43/3.4 C1/0.7 110/120 5 A5/10B1-43/3.4 C1/0.7 110/120 6 A6/10 B1-43/3.4 C1/0.7 110/120 7 A7/10B1-43/3.4 C1/0.7 110/120 8 A8/10 B1-43/3.4 C1/0.7 110/120 Compar. A1/10  BX1/3.4 C1/0.7 110/120 comp 1

In Table 1, each of characters represents the following component:

<Resin>

A1: Resin A1, A2: Resin A2, A3: Resin A3, A4: Resin A4, A5: Resin A5,A6: Resin A6, A7: Resin A7, A8: Resin A8,

<Acid Generator>

B1-43: Salt represented by formula (B1-43), produced according to themethod as recited in JP2016-47815A1

BX1: Salt represented as follow, manufactured by WAKO Pure chemicalcorporation

<Quencher>

C1: The compound of the following formula, produced according to themethod as recited in JP2011-39502A1

<Solvent>

Mixture of the following solvents propyleneglycolmonomethylether acetate400 parts propyleneglycolmonomethylether 150 parts γ-butyrolactone 5parts

<Evaluation: Alkali Development>

6 inch-diameter Silicon wafers were each coated withhexamethyldisilazane and then baked at 90° C. for 60 seconds using adirect hotplate.

Each of the photoresist compositions prepared as above was spin-coatedover the coating so that the thickness of the resulting film became 40nm after drying. The silicon wafers thus coated with the respectivephotoresist compositions were each prebaked on a direct hotplate at thetemperature as listed in the column “PB” of Table 1 for 60 seconds.Using an EB straight-writing system (HL-800D 50 keV manufactured byHITACH), line-and-space patterns were produced on the composition layerwith the exposure quantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at the temperature as listed in the column “PEB” of Table 1for 60 seconds and then to development for 60 seconds at 23° C. with2.38% by mass aqueous tetrametylammonium hydroxide solution in themanner of paddle development to produce positive photoresist patterns.

Effective sensitivity (ES) was defined as the exposure quantity withwhich exposure provides a pattern with 60 nm of the line width afterdevelopment, the pattern being observed with a scanning electronmicroscope.

Determining Line Edge Roughness:

The line-and-space patterns were produced according to theabove-mentioned procedure in which the exposure step was conducted atthe effective sensitivity.

The wall surface of the photoresist pattern was observed using ascanning electron microscope, and the irregularity in wall surface wasdetermined. Here, the roughness width means the difference of thelargest value and the smallest value as to the wall width.

Table 2 illustrates the results thereof.

The figures mean roughness width values (nm).

TABLE 2 Ex. No. Composition No. LER value (nm) Ex. 1 1 4.12 Ex. 2 2 3.76Ex. 3 3 4.18 Ex. 4 4 3.75 Ex. 5 5 3.72 Ex. 6 6 3.82 Ex. 7 7 3.79 Ex. 8 83.74 Comp. Ex. 1 Compar. Comp. 1 5.68

<Evaluation: Butyl Acetate Development>

6 inch-diameter Silicon wafers were each coated withhexamethyldisilazane and then baked at 90° C. for 60 seconds using adirect hotplate.

Each of the photoresist compositions prepared as above was spin-coatedover the coating so that the thickness of the resulting film became 40nm after drying. The silicon wafers thus coated with the respectivephotoresist compositions were each prebaked on a direct hotplate at thetemperature as listed in the column “PB” of Table 1 for 60 seconds.Using an EB straight-writing system (HL-800D 50 keV manufactured byHITACH), line-and-space patterns were produced on the composition layerwith the exposure quantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at the temperature as listed in the column “PEB” of Table 1for 60 seconds and then to development for 20 seconds at 23° C. withbutyl acetate in the manner of dynamic dispense method to producenegative photoresist patterns.

Line edge roughness of the negative photoresist patterns was determinedin the same manner as that of the positive photoresist patterns. Table 3illustrates the results thereof.

The figures mean roughness width values (nm).

TABLE 3 Ex. No. Composition No. LER value (nm) Ex. 9 1 4.26 Ex. 10 23.70 Ex. 11 3 4.30 Ex. 12 4 3.82 Ex. 13 5 3.79 Ex. 14 6 3.48 Ex. 15 73.74 Ex. 16 8 3.65 Comp. Ex. 2 Compar. Comp. 1 5.78

The composition of the present invention can provide photoresistpatterns with smaller LER, and is suitable for fine processing ofsemiconductors.

1. A photoresist composition comprising a resin which comprises astructural unit represented by the formula (I):

wherein R¹ represents a hydrogen atom or a methyl group, R² represents aC1-C6 hydrocarbon group, Ar represents a C6-C36 divalent aromatichydrocarbon group in which a hydrogen atom can be replaced by asubstituent, R³ represents a hydrogen atom or an acid-labile group; anda salt represented by the formula (B1):

wherein Q^(b1) and Q^(b2) independently each represent a fluorine atomor a C1-C6 perfluoroalkyl group, L^(b1) represents a C1-C24 divalentsaturated hydrocarbon group in which a methylene group has been replacedby —CO—, in which a methylene group can be replaced by —O— and in whicha hydrogen atom can be replaced by a fluorine atom or a hydroxyl group,Y represents a methyl group in which a hydrogen atom can be replaced bya substituent or a C3-C18 alicyclic hydrocarbon group in which ahydrogen atom can be replaced by a substituent and in which a methylenegroup has been replaced by —O—, —S(O)₂— or —CO—, and Z⁺ represents anorganic cation.
 2. The photoresist composition according to claim 1wherein the acid-labile group is represented by formula (1a) or (2a):

in which R^(aa1), R^(aa2) and R^(aa3) independently each represent aC1-C8 alkyl group in which a hydrogen atom can be replaced by asubstituent, a C3-C20 alicyclic hydrocarbon group in which a hydrogenatom can be replaced by a substituent, “naa” represents an integer of 0or 1, and * represents a binding position;

in which R^(aa1′) and R^(aa2′) independently each represent a hydrogenatom or a C1-C12 hydrocarbon group, and R^(aa3′) represents a C1-C20hydrocarbon group, X^(a) represents an oxygen atom or a sulfur atom,and * represents a binding position.
 3. The photoresist compositionaccording to claim 1 wherein Ar represents a phenylene group.
 4. Thephotoresist composition according to claim 1 wherein R³ represents ahydrogen atom or a group represented by formula (2a).
 5. The photoresistcomposition according to claim 1 wherein the resin further comprises astructural unit having an acid-labile group.
 6. The photoresistcomposition according to claim 5 wherein the structural unit having anacid-labile group is represented by formula (a1-1) or (a1-2):

wherein L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7 and *represents a binding position to —CO—, R^(a4) and R^(a5) eachindependently represent a hydrogen atom or a methyl group, R^(a6) andR^(a7) each independently represent a C1-C8 alkyl group, a C3-C18alicyclic hydrocarbon group, or a group formed by combining them, m1represents an integer of 0 to 14, n1 represents an integer of 0 to 10and n1′ represents an integer of 0 to
 3. 7. The photoresist compositionaccording to claim 6 wherein the resin further comprises the structuralunit represented by formula (a1-1) and the structural unit representedby formula (a1-2).
 8. The photoresist composition according to claim 1which further comprises a salt generating an acid weaker in acidity thanan acid generated from the acid generator.
 9. The photoresistcomposition according to claim 1 which further comprises a resincomprising a structural unit having a fluorine atom.
 10. A process forproducing a photoresist pattern comprising the following steps (1) to(5): (1) a step of applying the photoresist composition according toclaim 1 on a substrate, (2) a step of forming a composition film byconducting drying, (3) a step of exposing the composition film toradiation, (4) a step of baking the exposed composition film, and (5) astep of developing the baked composition film, thereby forming aphotoresist pattern.